1 Introduction

Rapid urbanization, increasing populations, and modernization generate a large fraction of solid waste which is of major concern for worldwide treatment and management companies, environmental committees, and government agencies (Voukkali et al. 2023). Solid wastes are extremely varied due to the different sources of generation and rates of disposal practices in various cities of developing countries (Abdel-Shafy and Mansour 2018). Waste collection, transportation, and management by landfilling is an expensive and unattractive treatment provision with high principal management costs (Parthasarathy et al. 2022). Also, managing solid waste became a focal point to confirm the achievement of energy-water-food nexus in the coming future (Boechat et al. 2017). It is forecasted by FAOSTAT (2019) that urban residential waste generation will increase by 4.3 billion tons worldwide in 2025 which is a big threat for living beings, environment and sustainable waste management system (Boechat et al. 2017).

Recycling of solid waste to biochar is a sustainable approach and has been a widely accepted soil amendment to improve soil quality, mitigate climate change, and enhance carbon sequestration (Shikha et al. 2023). Biochar could be efficient to reduce almost 10% to 12% of world greenhouse gas (GHG) emissions from crop fields, grassland, and forest land. Biochar is also a good rhizobium bacteria barrier between soil microbiota and nutrient cycles which has a positive impact on soil texture, plant growth and crop yield. Additionally, biochar has the potential to maintain other GHG like nitrous oxide (N2O) and methane (CH4) by inducing them into alternative favorable chemicals for soil and plants (Shikha et al. 2023).

1.1 Contribution of food waste from organic solid waste

Among all different types of solid waste, organic wastes constitute the highest fraction and consists of tree wood and bark, grass, garden, farm waste, and greenhouse waste, along with a large fraction of food waste (Bustamante et al. 2016; Haynes et al. 2015; Wei et al. 2017). Organic solid waste is generally biodegradable in nature, but it requires a long time period to decompose. Also, decomposed organic waste creates a nuisance in nature (Awad et. al 2017), has negative impact on aesthetics and beauty, raises the risk of fire and methane (CH4) gas production, and is harmful to the climate condition (Kan et al. 2017; Shi et al. 2021). The massive rise of organic waste became an obstruction on the municipal waste management budget, which encourages the recycling of organic waste to technoeconomic sustainable product.

Amongst all the organic waste, food waste contributes the highest portion (more than 50%) of the total organic waste generated worldwide except Central Asia, Europe, and North America, which have higher portions of dry waste. According to Nordin et al. (2020) and UNFAO (2021), among all types of organic waste, globally almost 1.3 billion tons of food waste is generated per year by human consumption. Almost 670 million tons (mT) and 630 mT of edible foods are discarded by 1.4 to 6.2 billion people in developed and developing countries (Amicarelli and Bux 2021; UNFAO 2021).

Food waste management is one of the major environmental concerns at every stage of the food supply chain. Food waste is a relatively high lignocellulose component which consists of approximately 27% to 57% cellulose, 11% to 55% hemicellulose, and 3% to 22% lignin on a dry basis (Cao et al. 2018; Langsdorf et al. 2021). Therefore, food waste transformation into value added bioproduct by different recycling technologies could improve the bioeconomy by promoting the transition of a circular economy (Zeller et al. 2020). Many management methods are used for food waste disposal but have faced numerous challenges such as the generation of toxic byproducts, high costs, and environmental pollution.

1.1.1 Impact of food waste generation and economical aspects

Typically, both edible and nonedible food waste are generated in every step of food supply chains from post-harvesting, industrial processing, and delivering to retailers and consumers (UNFAO 2021). The sociodemographics of households also play a major role in many food waste generation such as bread, dairy products, fruit, and vegetables among consumers. Inadequate food waste transportation and disposal strategy significantly influence the economy, condition of living beings, and environmental pollution rate. According to a survey in India, due to the extremely weak post-harvest infrastructure, more than 30% of vegetables and fruits are spoiled (Mahajan and Vakharia 2016). According to a survey by UNFAO (2021) almost 23 million tons of grain, 12 million tons of fruits, and 21 million tons of vegetables were lost with a total value of 4.4 billion USD$ out of a total food waste of 10.6 billion USD$. In many regions of Africa, approximately 25% of grains and 50% of fruits and vegetables were lost out of total farm production after post-harvesting.

Figure 1 represents per capita food lost from production to retailing and by regional consumers in economically developing countries (UNFAO 2021). It is observed from Fig. 1a that maximum fruit and vegetable were wasted in South and Southeast Asia during packaging and transport, while in Europe, North America and Oceania, huge quantity of food is damaged during agricultural harvesting and negligible waste throughout the transformation and packaging by consumer level. The tangible impacts due to food waste in the form of different commodities and impacts on cost were analyzed and shown in Fig. 1b and c. It is also estimated that the carbon footprint due to food waste was almost 3.3 billion tons of carbon dioxide (CO2) emission per year. For various commodity groups in Fig. 1b, it is observed that land occupation is high for meat, milk, and grains; however, the GHG emissions patterns are high for meat, milk, grains, and vegetables. But maximum economic value was observed for meat, fruit, and starchy roots (Fig. 1c).

Fig. 1
figure 1

(a) Global generation of food wastes and carbon food print, (b) key impacts of food waste commodity and (c) costs of loss due to environmental factors by different commodity groups. EU: Europe; NAO: North America and Oceania; IA: Industrialised Asia; SSA: Sub-Sahana Africa; NA: North Africa; WA: Western Asia; CA: Central Asia; SSA: South and Southeast Asia; LA: Latin America; GHG: greenhouse gas; SR: starchy roots; VEG: vegetables; OCL: oilcrops and legumes; FSF: fish and sea foods

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1.1.2 Food waste from farm and impact on environment

According to a survey report in 2021, food production from farm sector plays a major role globally and approximately 1.2 billion tons of food is lost in the farms each year, which is almost 15.3% of the global food production (Adejumo et al. 2020; UNFAO 2011; FAO 2017). Due to insufficient skills, lack of technology, poor infrastructure, logistics, storage capacity and lack of market place, the nonedible fruit, vegetables and crops are rotten because of severe rainfall and high heat in summer (Dien and Vong 2006). Another cause is an inadequate road network for transporting harvested food from farm to market or cold store in many developing countries (Obi et al. 2016). Many farmers largely depended on solar drying before storage. Sometimes incomplete drying leftover moisture in grain and nuts resulted in food infection by storing a long time period. Also, larger scale market place, fair and supermarkets played a major role in overproduction in artistic food production in the farms all over the world. As a result, large quantities of vegetables and fruits are forced to be thrown away due to lack of aesthetic beauty. Johnson et al. (2018) reported almost 42% of vegetables were lost in nine farms by the primary production stage in North Carolina, USA in 2018 which is two times higher than 2011 estimated data of 20% (Gustavsson et al. 2011). In European Union (EU) it was pointed that 24.5 Mt of fruit and vegetable were wasted during the primary production stage of the farm which is much higher than 2011 (Caldeira et al. 2019). While Xue et al. (2021) reported that 77% of food waste was generated from household during the consumption stage among which fruit and vegetable wastes were the highest.

Food waste from farmyards and in dumping lands also intensifies the climate change crisis with significant GHG emission. It has been documented that about 24% of GHG is emitted from agriculture each year (Rahman et al. 2021; USDA 2022). Leftover untreated food waste and improper disposal destroy biodiversity near by the farmland and cause serious threat to human health. Additionally, application of excess pesticides and fertilizers to enhance crop and vegetable production also leads to discharged of toxic compounds by irrigated water and rainwater which contaminate soil, water, food, and aqua life directly (Lahlou et al. 2023). Therefore, focusing on serious issues due to food waste and reducing economic loss in each stage from transportation to landfill, valorization of food waste to technoeconomic products are critical for ecofriendly environment.

1.1.3 Obligation of food waste management

Crop, fruit and vegetables are highly water demanded and as a result they end up with wasting a plenty of fresh water in the form of uneaten food. Approximately 220 billion USD$ is spent over growing, transporting and processing of fruit and vegetables out of which almost 172 billion USD$ is lost in the form of wastewater and 70 million tons of food waste ends up in landfills (USDA 2022). As per a study reported by previous study (Jayasiri et al. 2022), approximately 85% of the water that irrigates in rice fields in Java Island released 54 mg L−1 of nitrate (NO3−) which is 20% higher than the required water quality standard by the application of large quantity of fertilizers and pesticides. Additionally, improper management of drainage water will have adverse impact on declining the surface water quality (Dębska et al. 2021). The high intensity of agricultural activities reflects high concentration of nutrients particularly nitrogen in the form of nitrate (NO3−) and ammonia (NH3+) merged into the river waters and infiltrated into the groundwater (Lawniczak et al. 2016). It was signified that the high concentration of NO3− is the most common chemical contaminant in the world’s groundwater aquifers (Jayasiri et al. 2022).

Excessive discharge of food waste from different sources is a critical step for waste collection, transportation, and management. According to the National Environment Agency (NEA 2015), approximately 785,500 tons of food was wasted in Singapore, from which only 13% has been recycled and 681,400 tons of wastes were disposed by landfilling in 2015. Worldwide, this number is expected to rise by 50%. In the USA, 40% of food waste was generated each year and 95% finished up in landfill sites (Gupta et al. 2015). According to a survey in 2014, more than 38 million tons of food was wasted and only 5% diverted from landfills to composting, which results in generation of methane (CH4), a strong GHG that contributes to global warming due to decomposing food waste. Declining soil fertility and soil organic carbon (SOC) loss, intensive tillage and application of high inputs in conventional fruit and vegetable management have not resulted in productivity yield (Rahman et al. 2021). As a result, in 2012, high levels of 190 Mt CO2eq of GHGs were emission from the farm in Bangladesh. For instance, crop land including chemical fertilizers, and intensive tillage contribute to 20% of global GHG emission (Jantke et al. 2020).

1.1.4 Impact of food waste disposal on public health

Many studies have been focused on occupational health issues for human beings, animals, and birds particularly those living near the waste dumping site. In addition to carcinogenicity, many elements present in decomposed food waste could affect neuro system, liver, kidneys, lungs, heart, skin, and reproduction (Nandomah and Tetteh 2023). A substantial emission of pollutants such as sulphur dioxide (SO2) and particulate matter (PM10) from food waste in landfilling area increases air pollution and have an impact on morbidity and mortality. Vianna and Polan (1984) reported that people staying near landfill sites face the risks of a child having a birth weight lower than 2.5 kg, fetal issue, newborn mortality, spontaneous miscarriage, and birth defects rates. From 1971 to 1975, a similar case of low birthweight was found among those living near landfilling site within a 1 km radius of the Lipari landfill in New Jersey and also in California (Kim et al. 2020; Kharrazi et al. 1997). In Great Britain, lower weight childbirth was noticed within a 2 km radius of a landfill site from 1982 and 1997 in addition to excess risk of skin irritation, gastrointestinal problems, respiratory symptoms, psychological problems, nose and eyes, fatigue, headaches, and allergies among mothers during delivery operation or after delivery.

Focusing on these serious issues, many researchers adopted an innovative and sustainable approach towards food waste valorization to reduce load on landfilling. However, more review is essential on food waste valorization to create a value-added product for application in agriculture production, improving soil quality, enhancing water and nutrient retention, and remediating environmental pollution.

1.1.5 Advantages and disadvantages of food waste management processes

Food waste contains high moisture, cellulose, hemicellulose, carbohydrates, and fats that require distinct treatment technologies. Common traditional treatment practices for handling food waste include landfill, incineration, anaerobic digestion, and composting (Gao et al. 2017; Rushton 2003). Landfilling is a widespread and easiest technique to dispose food waste with the disadvantages of lack of land availability, land prices, especially when considering increasing compliance costs, leachate management, public opposition, and greater GHG emission. In landfill sites, many animals also used food wastes as a feed in many countries and faced fever, foot and mouth diseases by viruses infection due to the incomplete treatment of livestock or mixed with meat (Elkhalifa et al. 2019; Salemdeeb et al. 2017). Additionally, the major challenge is the requirement of high costs for collecting food waste and transportation. Incineration is one of the food waste recycling techniques which can be used to incinerate large volume of food waste to produce thermal energy (Gao et al. 2017). But the major drawback are the high installation cost of incinerators, higher risk for long-term negative health impacts on the communities near the incineration plant and the requirement of consistent and enduring feed for optimal operation. The burning process in incinerators can pollute the environment if not properly operated and monitored. It could impact human health for a long time by developing complications such as genetic disabilities and cancer. After incineration, the end product “ash” also contains several toxic compounds and heavy metals that may be potentially harmful to the people during the recovery process (Jacob et al. 2021; Kalmykova and Karlfeldt Fedje 2013).

Recycling of food waste to composting is an efficient way to provide an ideal environment to improve soil fertility, and microbial activity, and reduce GHG emission (Kumar et al. 2010). Although there are many benefits, the major drawbacks of this process are requirement of a large area for composting, long reaction time to decompose, high costs for food waste collection and transportation (Jouhara et al. 2017). An extensive range of food waste is also recycled through anerobic fermentation which is a suitable metabolic process leading to the biogas production in the absence of oxygen (Jia et al. 2017). But the major challenges are construction and installation of biogas fermentation plants that require huge capital cost to procure equipment, exact startup condition and requirement of long time to ferment (De Baere 2006). Additionally, during fermentation process a large quantity of toxic sulfur compounds are generated (Chen et al. 2008). Due to the drawbacks of these conventional waste treatment strategies, it is important to develop an efficient and sustainable food waste management plan. The method should be viable, especially when the land availability for the process is limited and economical.

The thermochemical process, pyrolysis, is a simple and convenient way to reduce more than 80% of the total volume of waste and has recently gained interest for the food waste recycling supporters. It offers a shorter reaction time and allows for increased energy recovery efficiency for various types of food wastes (Czajczyńska et al. 2017). Pyrolysis processes thus represent a useful technique for the food waste conversion to energy and may also minimize environmental impacts (Ghiat et al. 2022). Compared to incineration, the pyrolysis process is more flexible simply by varying of two operating parameters such as temperature or heating rate, and emits negligible concentrations of air pollutants, such as polybrominated diphenylethers (Chen et al. 2014).

1.1.6 Pyrolysis process

The pyrolysis process involves the thermochemical conversion of carbon-based compounds into gas, liquid, and solid products. Pyrolysis is the most admired technique due to cost-effectiveness, simplicity, and competence to progress a wide variety of feedstocks to produce biochar through the thermochemical conversion technique under an oxygen-deprived condition at elevated temperatures (Abdelaal et al. 2021; Elkhalifa et al. 2019; Parthasarathy et al. 2022; Pradhan et al. 2020b). Food waste originated from residence and farms can be converted to a valuable product biochar by pyrolysis process to retain nutrients, contribute to carbon sequestration and balance GHG to achieve independent carbon (Sial et al. 2019). Pyrolysis of food waste offers both fast and slow process at a temperature range from 300 to 900°C with promising advantage. The fast pyrolysis process is employed to increase the yield of liquid product, while slow pyrolysis process is employed to maximize the yield of solid products and comparably higher than gasification (Al Arni 2018; Mavukwana et al. 2021).

Pyrolysis temperature, residence time and heating rate are major factors that influence the structural and physicochemical properties such as pore structures, surface area, elemental compositions and surface functional groups of biochar (Zuhara et al. 2023). The impact of pyrolysis temperature on biochar properties is recognized as the release of volatile matter at higher temperature (Parthasarathy et al. 2022) and slow pyrolysis temperatures lead to an increase in the surface area of biochar (Mariyam et al. 2023), pH (Shi et al. 2013; Hossain et al. 2011), and carbon (C) content by balancing nitrogen (N) content (Zhang et al. 2017). Thus, for pyrolysis of food waste, selecting the appropriate temperature is promising for the structural and chemical properties of biochar for agriculture productivity, soil water pollution remediation and GHG emission mitigation. Many studies reported that the food waste biochar properties produced at a medium and higher pyrolysis temperature are beneficial for removing organics, inorganics, metals, and heavy metals from wastewater, while at lower pyrolysis temperature, it is advantageous for agriculture production, and soil contamination remediation (Mariyam et al. 2023; Pradhan et al. 2020a; Zhang et al. 2017).

Boakye et al. (2023) produced biochar from mixed vegetable wastes by pyrolysis process at a temperature range from 300°C to 600°C and observed that biochar at 300°C has high nitrogen and organic matter content with lower yield and bulk density. The biochar amendment of 17% to 60% produced at lower temperature is beneficial as it increases maize grain yields of 28% and leads to longer root length by increasing nutrients such as calcium (Ca), magnesium (Mg), phosphorous (P), and potassium (K). The thermal conversions of food waste by pyrolysis process are beneficial and widely acceptable by achieving extensive reduction of pollutants and resource recovery (Pradhan et al. 2020a; Zhao et al. 2022). Pyrolysis technology is more comprehensive in organic pollutants from food waste than other hydrothermal technologies and produced biochar for extensive range of field applications (Dutta et al. 2021). Additionally, the pyrolysis process also helps to reduce GHG emission and the volume of waste disposed in landfills (Kwon et al. 2020). Based on the benefits and the repetitive materialization of modern scientific accomplishments, a detailed review on the pyrolysis of food waste, impact of pyrolysis temperature on biochar properties and useful applications is highly needed.

1.1.7 Motivation of food waste recycling

Many countries are focusing on the issues due to huge generation of food waste at national level (Cesaro et al. 2015; Pradhan et al. 2020a) and undertaking steps towards a water-food-energy nexus approach (Al-Ansari et al. 2017). Food waste contains various compounds such as variety of organics, carbohydrates, amino acids, phosphates, and vitamins that make it a promising resource for agriculture production (Chew et al. 2018). A food waste remediation prospect associated with pyrolysis brings new ecofriendly ventures to produce biochar with an agricultural and food process industries’ profitability approach. Biochar production and application for environmental remediation, carbon sequestration, wastewater and soil treatment, soil quality improvement, soil microbial enrichment and plant growth are practical approaches to mitigate climate change (Beesley et al. 2011; Pradhan et al. 2022; Rahman et al. 2021; Shikha et al. 2023). However, limited studies have reported the impact of the pyrolysis process on biochar properties produced from various types of food wastes (Ahn et al. 2023; Boakye et al. 2023; Ismail et al. 2023; Makkawi et al. 2022; Raček et al. 2024). Many research studies elaborated on biochar production from different biomass and their application in different environmental practices (Shikha et al. 2023). But a very few reviews have reported precisely on food waste biochar produced at different pyrolysis temperatures on soil quality improvement, plant growth, yield of crop, soil microbial activity and remediation of GHGs emission (Beesley et al. 2011; Elkhalifa et al. 2019; Ismail et al. 2023; Yuan et al. 2023).

Therefore, this review attempts to fill in the knowledge gaps on the impact of different pyrolysis temperatures on various physicochemical properties of biochar production from food waste towards agriculture production and soil–water remediation. This study also aims to report a precise study on the impact of biochar produced at different pyrolysis temperatures on plant growth, mitigation of soil water stress and nutrients management. The review also summarizes the different characteristics of biochar produced by pyrolysis processes on the improvement in crop yield and soil microbial activity in different types of soil. This study conducted a detailed mechanism of biochar, soil, microbes and plant interaction in agriculture land to improve plant growth. Additionally, there is insufficient information available on economical aspects of biochar application to agriculture soil. Thus, this review elaborates on the economical analysis of biochar application for the production of different crops. This review also discusses current challenges that deteriorate the beneficial utilization of food waste by pyrolysis process, indicates some limitations and encourages future research prospectives to facilitate more improvement in pyrolysis techniques to produce high quality of biochar and application in environmental and agricultural practice.

2 Biochar as a remedy

Biochar is an affordable carbonaceous amendment and replacement of activated carbon to resolve the organic waste management issues (Zhang et al. 2012). Biochar produced from food waste and their physicochemical properties are considerably dependent on the types of food waste used as a feedstock (Amalina et al. 2022; Liu et al. 2020). Currently, biochar application as a soil amendment is most demanding and needy to improve soil quality due to the beneficial soil amendment properties. This study analyzed and described briefly the variability of physicochemical properties of biochar produced from various types of food waste feedstock at different pyrolysis temperatures in the sections below.

2.1 Influence of pyrolysis temperature on food waste biochar production

During the pyrolysis of solitary and blended food waste biomass, existence of volatile matters undergoes cross linking, depolymerization and fragmentation process at a specific pyrolysis temperature ranging from 300 to 600°C to produce a productive biochar for agriculture practice, soil quality improvement and water pollution remediation (Pradhan et al. 2020a; Raček et al. 2024). The efficiency of biochar produced from slow pyrolysis process for agriculture and environmental practice is strongly influenced by the moisture content of feedstock, size of the feedstocks, heating rate and residence time pyrolysis process (Ippolito et al. 2020; Pradhan et al. 2020a; Punsuwan and Tangsathitkulchai 2014; Zhao et al. 2018).

Some of our previous studies indicated that biochar produced from individual vegetable wastes, mixed vegetable waste, fruit waste and beverage wastes at different temperatures ranging from 300 to 600°C has suitable properties for agriculture production, water retention and water pollution remediation (Abdelaal et al. 2021; Al-Awadhi et al. 2022; Pradhan et al. 2020a, 2022). Our previous research studies reported that the biochar produced through a slow pyrolysis process at lower temperatures between 400 and 450°C has beneficial properties for chickpeas (Cicer arietinum L.) growth and grass (Poaceae) growth. Pradhan et al. (2020b) conducted a study on optimization of biochar produced from waste cabbage biomass by considering three design factors, namely, pyrolysis temperature, feed particle size, and quantity by slow pyrolysis process for agriculture application by response surface methodology (RSM). This study demonstrated that the biochar produced at a lower temperature of 360°C with particle size of 0.90 mm and a relatively low quantity of feed stock have beneficial properties for Ipomea (Ipomoea purpurea) plant growth in sandy soil. Likewise, some other reported studies also revealed the impact of pyrolysis temperature on food waste biochar properties. Islam et al. (2019) reported a positive influence of lower pyrolysis temperature on banana peel to produce biochar and its application on plant growth to overcome the use of chemical fertilizer. They recommended that pyrolysis process is an effective way to recycle food waste. Also, Sun et al. (2022) reported that pyrolysis process has the potential for egg shell to produce an biosorbent for slow release of nutrients from biochar and phosphorus recovery from the soil. Moreover, we focused on the impact of pyrolysis temperature on various physicochemical properties of biochar produced by different types of food waste feed stock and briefly summarized below what was reported previously.

2.2 Influence of pyrolysis temperature on biochar properties

2.2.1 Yield and ash content

The yield of biochar is an important key parameter to understand the mechanisms of reduction of volatile compounds from biomass during pyrolysis (Abdelaal et al. 2021; Hidayat et al. 2023). Figure 2a represents biochar yields produced from various food waste biomass at different pyrolysis temperatures conducted by many researchers. The results indicate that the yield of biochar from each feedstock decreases by increasing pyrolysis temperature due to the molecules present in char being broken down to produce smaller particles that improve the gaseous phase. The yield of biochar for all feedstock types is highest at the lowest temperature, which signifies that more components in the biomass reacted substantially with the increasing temperature but degraded differently to produce distinct product distributions at the corresponding temperatures. Whereas the ash content of the biochars shows contrast behavior to the yield and increases with rising temperature (Fig. 2b).

Fig. 2
figure 2

Effect of pyrolysis temperature on (a) yield and (b) ash content of biochar produced from various food wastes. PP: pea pods (Stella Mary et al. 2016); CL: cauliflower leaves and OP: orange peels (Stella Mary et al. 2016); DS: date seed (Joardder et al. 2012); AFWR: anaerobically digested food waste biogas residues (Alghashm et al. 2018); BP: banana peel (Pradhan et al. 2020a, b); HC: Hamlin citrus (Jafri et al. 2018); AA: alfa alfa (Kalus et al. 2019); CFW: cauliflower wastes (Pradhan et al. 2020a, b); CC: corn cob (Pradhan et al. 2020a, b); CW: cabbage waste (Pradhan et al. 2020a, b); SFW: salty food waste (Lee et al. 2017a, b); PH: peanut hull (Kalus et al. 2019; Laghari et al. 2016); BSG: brewer spent grain (Yinxin et al. 2015); CFS: coconut flesh shell (Suman and Gautam 2017); PR: potato residue (Liang et al. 2016); RSW: Rap seeds waste (Angın and Şensöz 2014)

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Biochar produced at higher pyrolysis temperatures generates higher ash content and minerals concentration by degrading volatile lignocellulose matters (Kalus et al. 2019). The variation in mineral content of biochar varied with ash content after clustering the cumulative losses of the volatile components (Novak et al. 2009; Novotny et al. 2015). Therefore, the range of ash content widely varied with the feedstock types and pyrolysis temperature (Igalavithana et al. 2017). High ash content increases the biochar pH, reduces nutrient availability and decreases the microbial population due to its alkalinity nature (Steiner et al. 2016) which results from microbial biomass degradation and N mineralization in the biochar amended soil produced at high pyrolysis temperature. However, the potential of liming should not only be related to the ash content, but also to the surface functional groups of biochar.

2.2.2 pH, ζ-potential and CEC

Th pH, ζ (Zeta) potential, and CEC (cation exchange capacity) are the major potential factors of biochar to enhance soil quality and microbial activity, which supports the boost of the plant growth and treatment of contaminated soil and water (Fig. 3). However, these three factors of biochar are highly depend upon pyrolysis temperature with biomass type and functional groups present in the biomass (Alotaibi and Schoenau 2019). Observation made from Fig. 3a shows that the pH of biochar produced from various types of food waste is highly influenced by pyrolysis temperature. All the biochar is alkaline in nature with pH ranging from of 7 to 12 at a temperature from 300 to 600°C (Qi et al. 2017). The release of phosphate (PO43−) and ammonia (NH3+) is highly influenced by the pH of the biochar, while potassium (K+) and nitrate (NO3−) concentrations are slightly dependent (Wang et al. 2015). The release of PO43− and NH4+ from the biochars increases the soil pH level when amended with biochar of pH ≤ 8, although K+ remains stable. This implies a greater benefit of biochar amendment for acidic nature of soil rather than the alkaline soil. Similarly, the persistence of Ca and Mg emission from biochar is also pH-dependent and reveals an increase in concentration corresponding from the reduction in pH of 8.9 to 4.5. The biochar amendment is beneficial for some soils of lower pH to maintain the alkalinity of the soil and to reduce the exchangeable aluminium (Al3+) (Butnan et al. 2015). Ultimately, pH of biochar affects minerals released to the soil, microbial activity and electrokinetic phenomenon after blending with the soil.

Fig. 3
figure 3

Effect of pyrolysis temperature on (a) ζ-potential, (b) pH and (c) CEC of biochar produced from various feedstocks. CC: corncob (Pradhan et al. 2020a, b; Yinxin et al. 2015); WR: wheat residue (Yuan et al. 2011); RH: rice hull (Yuan and Xu 2011; Kalus et al. 2019); CS: coconut shell (Zhao et al. 2019); PH: peanut hull (Kalus et al. 2019); CFW: cauliflower waste (Pradhan et al. 2020a, b); CW: cabbage waste (Pradhan et al. 2020a, b); FBW: faba bean peel (Krenz et al. 2023; Mukherjee and Lal 2013); DS: date seed (Joardder et al. 2012); OP: orange peel (Abdelaal et al. 2021); BP: banana peel (Pradhan et al. 2020a, b); PR: potato residue (Liang et al. 2016); MBP: moong bean pod (Yuan et al. 2011); ES: egg shell (Zhou et al. 2019a, b); GL: glucose; SU: sucrose; XY: xylose (Tran et al. 2016); RH: rice hull (Yuan et al. 2011); FP: fava bean peel (Mukherjee and Lal 2013); PS: peanut shell (Laghari et al. 2016); SFW: salty food waste (Lee et al. 2017b); SS: soybean shell (Mukherjee and Lal 2013); WB: wheat bunch (Yuan et al. 2011); POB: pam oil bunch (Lee et al. 2017a); SB: sugarcane bagasse (Sohaib et al. 2017)

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The electrokinetic phenomenon is the phenomenon of charged solids in shear plane and measured by ζ-potential. As an interfacial parameter, ζ-potential of biochar is highly influenced by the properties of the solid surfaces and the adjacent liquid (Qi et al. 2017). Different behaviors of ζ-potential of biochar produced from various types of food wastes were observed at different pyrolysis temperatures (Fig. 3b). The ζ-potential of some biochars increases with increasing temperatures, whereas for some biomass, it is vice-versa. The ζ-potential is highly influenced by the biochar pH (Yuan and Xu 2011). The range of pH from 3 to 7 carried a negative surface charge and more negative ζ-potential value occurred at a higher pH (Fig. 3c). Addition of biochar to the soil improves the electrochemical properties of the roots and increases nutrients uptake by two important factors such as ζ-potential and CEC (Farhangi-Abriz and Ghassemi-Golezani 2023).

The main mechanism of soil quality improvement, water and nutrient holding capacity, seeds germination and plant growth by applying biochar is because of one major factor, CEC (Alotaibi and Schoenau 2019; Wang et al. 2015). Figure 3d signifies that the CEC of biochar is higher at a temperature range from 300 to 500°C and lowest at higher temperatures more than 600°C due to the loss of functional groups and the oxidation of aromatics. However, there is no particular trend for CEC with pyrolysis temperature (Fig. 3d). Zhao et al. (2017) reported that the CEC of alkaline biochar is more efficient to uptake cationic nutrients. The amendment of biochar to the soil enhances pH and CEC of soil due to the slow release of alkaline substances, including ash and carbonates of Ca2+, K+ and Mg2+ (Dai et al. 2013; Wang et al. 2015). The biochar loading to the soil reduces the surface exchangeable acidic Al3+ and hydrogen (H+) cations due to the exchange ability of biochar which is beneficial for the crop growth.

While a study conducted by Mukherjee et al. (2011) for pH and CEC of biochar to observe the variation between pH and CEC produced at a temperature range from 250 to 650°C, but no trend was noticed between CEC and pH. Also, Lu et al. (2018) did not observe any dependency of CEC on ζ-potential or pH. As these three factors of biochar are linked with each other, more research is needed to examine the correlation between pH, CEC and ζ-potential at different pyrolysis temperatures by selecting more food waste biomass which has not been studied.

2.2.3 C/N, H/C, O/C ratio and BETSA

Biochar, as a soil amendment and adsorbent, is highly influenced by the ratio of (a) carbon to nitrogen (C/N), (b) hydrogen to oxygen (H/C), (c) oxygen to carbon (O/C) and (d) BET surface area (BETSA). Many observations were remarked on the variation of these properties with different pyrolysis temperatures for food waste biomass and shown in Fig. 4. The ratio of C/N is an indicator of soil fertility that refers to the ability of a soil to endure plant growth and high quality of yield (Conz et al. 2017; Kalus et al. 2019; Lee et al. 2017a, b). Under optimum C/N ratio of 18 to 24, soil microbes spur the release of nitrogen, phosphorus and zinc to crops (Bünemann et al. 2018). The wide C/N ratio leads to a slow degradation rate and nutrients immobilization and restricts microorganism activity due to existence of limited nitrogen in biochar. Nevertheless, limited C/N ratio, carbon and energy starvation occur. Brassard et al. (2017) reported that the C/N ratio in plant biomass helps to analyze the rate of decay and degree of available N released from the biochar (Brassard et al. 2017).

Fig. 4
figure 4

Effect of pyrolysis temperature on (a) C/N, (b) H/C (c) O/C and (d) BET surface area of biochar produced from various feedstocks. BP: banana peel (Pradhan et al. 2020a, b); CC: corn cob (Luo et al. 2018; Pradhan et al. 2020a, b); CFW: cauliflower waste (Pradhan et al. 2020a, b); CW: cabbage waste (Pradhan et al. 2020a, b); RH: rice hull (Yuan et al. 2011); PH: peanut hull (Kalus et al. 2019); CS: corn stove (Yinxin et al. 2015); DP: date palm (Jouiad et al. 2015); AA: alfa alfa (Lehmann et al. 2011); PKS: palm kernel shell (Ali 2018); OP: orange peel (Batista et al. 2018); SFW: salty food waste (Lee et al. 2017a, b); PR: potato residue (Yuan et al. 2011); RSW: rice straw waste (Yuan and Xu 2011; Kalus et al. 2019); WS: wheat straw (Yuan et al. 2011); RH: rice straw (Kalus et al. 2019); RAS: rapeseed waste (Karaosmanoǧlu et al. 2000); ES: egg shell (Sun et al. 2022); DS: date seed (Joardder et al. 2012); RSW: rapeseed waste (Gheorghe-Bulmau et al. 2022)

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Another indicator of biochar is the O/C ratio which signifies the polarity and abundance of polar oxygen containing surface functional groups in biochar. Higher O/C ratio affects the removal of pollutants especially adsorption of metals and heavy metals from soil (Harvey et al. 2011). In contrast, the H/C ratio indicates the aromaticity and stability of the biochar (Blasi 2002; Harvey et al. 2011) and an effective index for the adsorption of pollutants. In this study, the ratios of H/C and O/C biochars were analysed and reported in Fig. 4b and c. It was observed that both H/C and O/C ratios extensively decreased from 1.00 to 0.01 by increasing the pyrolysis temperature. The gradual reduction of H/C and O/C atomic ratios with increasing temperature is highly attributed to the dehydration reactions which signify the structural conversion and surface hydrophilicity of biochar (Tran et al. 2016). The higher extent of carbonization and loss of functional groups containing O and H (such as carboxyl and hydroxyl) at higher temperatures resulted in lower H/C and O/C ratios which indicates that the biochar surface is more aromatic and less hydrophilic (Batista et al. 2018). The H/C and O/C ratios are typically important for correlating the polarity and degree of aromaticity of the biochar. A higher O/C ratio of biochar is a good adsorbent and amendment that mainly indicates the presence of more functional groups (such as hydroxyl, carbonyl and carboxylate etc.) and contributes to higher CEC of biochar (Lee et al. 2017a, b).

The BET surface area, which is an important property of biochar for adsorption and water retention increases with rising pyrolysis temperature from 300 to 700°C for all types of food waste biochar due to complete carbonization (Fig. 4d). A greater surface area is suitable for improving a great extent of soil quality and water retention capacity (Shaaban et al. 2013). It was reported that the BET surface area is minimum (< 25 m2 g−1) for the biochars derived from all types of food wastes by the pyrolysis process at higher temperature. It could be due to pyrolysis reactor type, residence time, feedstock type and the size of the feedstock. Although biochar has lower BET surface area, it is still found to be impactful for soil water retention, nutrients uptake and pollutant removal (Pradhan et al. 2022; Wang et al. 2015). Thus, this study encourages production of biochar from different kinds of food waste by applying different conditions of pyrolysis which is directed to the future research scope of work. The above analysis signifies that pyrolysis temperature highly influences physicochemical properties of biochar from different types of food waste which could play a vital role for different applications in various aspects of agriculture and environment.

3 Biochar applications

3.1 Biochar for plant growth, yield and nutrient uptake

Numerous studies are reported on biochar applications produced from different types of food waste at different regions to improve soil quality, plant growth, water, and nutrition uptake (Table 1). The biochar application is favorable in extremely weathered tropical soils that are inadequate in quality due to a lack of numerous soil fertile properties and microbiological constraints. The most positive impact of food waste biochar is small fraction of biochar application to the soil improve soil water holding capacity, nutrients uptake capacity, plant growth and crop yield. This is due to the promising ability of biochar to constraint the nutrient leaching, control water loss by drainage and evapotranspiration, improvement in soil aeration and enhancement of microbial activities in different soil types (Zhang et al. 2013; Agegnehu et al. 2016; Pradhan et al. 2022). Most of the studies reported in Table 1 presents that the impact of biochar produced from various types of food waste improves agriculture production to a varying extent. These beneficial effects can also help to overcome land restoration and remediation.

Table 1 Impact of biochar application on plant growth, water and nutrient retention in different soil types
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Agegnehu et al. (2016) reported that the increase of crop yield is due to the increase in soil CEC and crop nutrients value by biochar amendment of the soil. Biochar amendment to the acidic soil is extremely beneficial to raise plant growth and crop production (Mensah and Frimpong 2018; Nair et al. 2017). The biochar produced from vegetable waste, nutshell, and fruit waste at a pyrolysis temperature less than 500°C is performing positively on plant growth, leaf development, crop yield, plant biomass, nutrients and water retention capacity. Thus, food waste biochar amendment is highly recommended for agriculture practice. This review will help extend selection of food waste biochar application at different doses in various types of soil and crops.

3.2 Biochar impact on soil microbial activity

Food waste biochar amendment to the soil may directly and indirectly influence the microbial activity in several qualities of soil which is described in Table 2. Development of microbial communities is supported by the provision of habitat and available carbon source from biochar (Ali et al. 2021; Palansooriya et al. 2019; Zheng et al. 2021). This study revealed the stability of biochar loaded soils and the relationship between soil organic matter acquisition and microbial activity. Food waste biochar application to the soil enhanced the community of nitrosospira, nitrosomonas, candidatus nitrotoga, glucosidase, phosphatase, urease activity, dehydrogenase activities, catalase activity and urease activity (Ali et al. 2021; Liu et al. 2023; Oladele 2019; Zheng et al. 2021; Zhou et al. 2023). Furthermore, the organic matter, physicochemical properties and nutrients in biochar may ultimately influence the soil microbial community. Relatively small fractions (1% to 2% w/w) of biochar are adequate to increase the water holding capacity by reducing soil bulk density of different soil which impact drying microbial community types (Mukherjee and Lal 2013; Pradhan et al. 2022). The soil pH is a key parameter that influences microbial activity (Wakelin et al. 2008). While fungi is dominant at lower pH and the bacteria are richer at higher pH (Bååth and Anderson 2003). A research study conducted in Japan and Germany has been revealed that biochar can complex the soil carbon from dead microorganisms (Luo et al. 2018). Biochar application is also beneficial for stimulating the dead persistent soil microorganisms that have a major role for achieving soil ecosystem engineering tasks, specifically for nutrient cycling and soil hydrology. Biochar can promote the activity of different soil microorganisms (Table 2), nevertheless there is a little evidence of research in this field.

Table 2 Assessment of biochar impact on soil microbial activity
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3.3 Mechanism of biochar, soil, microbes and plant interaction

Soil microbial populations and extracellular enzymes play a critical role in (a) decomposing organic matter and (b) nutrient and mineral cycling process. Both microbial and enzyme activities can change quickly in soil environment responses by changing nutrient cycling (Palansooriya et al. 2019; Yuan et al. 2019). Therefore, soil biochemical processes, soil quality, plant growth and pollutants removal from soil can be influenced by the changes of microbial communities or enzyme activities (Fig. 5). Based on some specific key functions of biochar, this review combines the mechanisms of biochar and microbe interaction for plant growth (Fig. 5). In general, the impact of microorganism interaction on biochar amended soil cannot be explained by a single protocol as biochar can affect soil beneficial microorganisms both positively and negatively (Laghari et al. 2016). Despite the slow rates of soil organic matter production compared to other streams in the carbon cycles, its comparative stability for microbial degradation assists with soil organic matter accumulation (Yu et al. 2009; Alotaibi and Schoenau 2019). There is growing interest in the biochar application to manage soil biota (Ding et al. 2016) and microbial properties are highly affected by the soil food web. Shikha et al. (2023) conducted a study on effects of biochar with the rhizobium biofertilizer on plant-soil interactions for soil microbes communities in the Charland agroecosystems in Bangladesh. The combined application of biochar and biofertilizer was beneficial for the growth of groundnut and yield. The biochar application boosted N nitrification and enhanced rhizobium involved in nitrification and denitrification. Therefore, in order to use biochar as a soil amendment, soil type and microorganism species must be considered.

Fig. 5
figure 5

Mechanism of plant growth due to the interaction between biochar, soil, microbes and plant. CEC: cation exchange capacity; EC: electrical conductivity; WRC: water retention capacity

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3.4 Economical aspects of biochar application in agriculture

Biochar has also received considerable scientific attention with regards to economic assessments for carbon storage and enhancing agricultural yields in the past decade. This study investigates the economic value of biochar as an amendment for short- and long‐term soil improvement. Keske et al. (2019) reported the economical benefits of biochar production from black spruce forests biomass and its application as a soil amendment to improve potatoes and beets production in Canada. The budget of biochar production through slow pyrolysis process estimates a fixed cost of $505.14 per mg, but after applying biochar to the soil for local potato and beet production, it makes the return of biochar profitable. Keske et al. (2019) reported that the beet yield was increased from 2.9 mg ha−1 to 11.4 mg ha−1 with an annual return profit of $11,288 ha−1 by applying 10 tons of biochar. While in the case of potato production, the net return profit was $965.48 ha−1. Biochar application offers a higher rate of return value for beets production than potatoes.

In another study, Laurentiis et al. (2018) and Galinato et al. (2011) reported that each ton of limestone transportation and application in the agriculture soil formed bicarbonates (HCO3−) and emitted 0.22 metric tons (MT) of CO2 from the agriculture land. This amount of emissions was potentially avoided by replacing lime with biochar and by using the CO2 offset price ranging from $1 to $31 MT−1 of CO2. Galinato et al. (2011) examined the potential economic returns to farmers by utilizing biochar as an amendment in agriculture for fewer than three price scenarios: (a) $114.05 MT−1, (b) $87 MT−1 and (c) $350.74 MT−1 based on the energy content of a waste wood biochar. According to EIA, the energy content of Central Appalachian coal is 12,500 BTUlb−1 and its price was $116.38 MT−1 in 2008 (EIA 2009). Using the energy content basis, the combustion value of biochar is 98% of Central Appalachian coal with a cost of $114.05 MT−1 (Dickinson et al. 2015).

3.5 Biochar for water quality improvement

Toxic contamination in aqueous solutions has become a prevalent problem throughout the world. The removal of organics and heavy metals by biochar is an important application due to its large specific surface area, surface functional groups and porous structure. Table 3 shows the biochar derived from different food waste used as a low-cost adsorbent for removal of organic pollutants that include dyes, antibiotics, pesticides, herbicides, metals and heavy metals from the polluted water (Ahmad et al. 2012; Mahmoud et al. 2012; Xu et al. 2011). Fruit and vegetable waste and nut shell biochar is highly effective, for it removes maximum of 1.84 to1666.67 mg g−1 of Pb, 6.5 to 493.34 mg g−1 of Cu, 68.23 mg g−1 of Cr, 49.0 mg g−1 of Ag 557.0 mg g−1 of P and 110 mg kg−1 of organics (Ahmad et al. 2012; Chen et al. 2011; Kumar et al. 2023; Wang et al. 2021; Xu et al. 2011). In the past few years, many studies reported that biochar produced from vegetable, fruit and nut peel biomass at different pyrolysis temperatures is beneficial for adsorption of various contaminants. Still, more studies are needed to improve pyrolysis condition by considering solitary and mixed food waste to enhance the adsorption capacity of biochar that could be beneficial for commercial wastewater treatment.

Table 3 Assessment of biochar impact on various organic and inorganic contaminants removal in polluted water
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3.6 Biochar for contaminated soil remediation

Similar to water pollution remediation, biochar is highly efficient, innovative and promising focus on soil contamination remediation focusing towards modern environmental clean-up strategies (Beesley et al. 2011; Liu et al. 2020). This study explored that food waste biochar application is extremely important for remediating organics and heavy metal pollution from contaminated soil (Jeffery et al. 2011) and is widely acceptable for sustainable development (Table 4). Many studies (Atkinson et al. 2010; Igalavithana et al. 2017; Shen et al. 2012; Tong et al. 2011; Zhang et al. 2019) reported that the benefits associated with the biochar application to the soils are not only related to its high organic carbon adsorption but also for Pb, Cu, As, Hg, Cd, Cr, etc. Food waste biochar is beneficial as a soil amendment for sorbing metals and nutrients and gradually releasing nutrients through increasing root density (Chen et al. 2016; Jiang et al. 2012).

Table 4 Assessment of pollutant removal from soil by biochar application
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3.7 Soil carbon sequestration

Soil organic carbon (SOC) is a critical indicator of sustainable crop land management and plays a vital role to increase crop yield, climate regulation, soil water and nutrient uptake (Nandwa 2001; Rahman et al. 2021). Increase in soil carbon storage by controlling emission has more inclusive benefits for protecting biodiversity, diminish food insecurity, and alleviating climate change for terrestrial ecosystems (Hamidov et al. 2018; Paustian et al. 2019). Biochar as a soil conditioner is beneficial in storing underground carbon inputs with deep rooted crops (Laird 2008; Chenu et al. 2019; Whitehead et al. 2018). Food waste biochar amendment to the soil not only promotes a direct SCQ strategy due to its high strength carbon storage and durability but is also beneficial for soil fertility (Paustian et al. 2019; Rahman et al. 2021; Rasul et al. 2022). Biochar could be used to reduce SOC decomposition by 44 to 365 kg C t−1 and improves carbon capture by plants (Chenu et al. 2019; Whitehead et al. 2018). Sial et al. (2018) reported that from their laboratory scale experiment that 2% banana peel biochar amendment enabled reduction of 24% of CO2 emissions from the soil compared with the control and suggested that it had the potential for mitigating GHG emissions in field condition. Ali et al. (2021) reported that application of 3% of corncob biochar produced at 400°C into the soil significantly increased 246% to 266% of the organic carbon in the soil compared to the control. Lee et al. (2010) reported a total size of the 1.411 million hectares (mha) of world’s arable crop land that potentially stored 428 giga ton carbon (GtC) by biochar. Approximately 34.2 to 84.3 GtC was stored in 112.5 to 277.5 mha arable land in South America, North America, Africa, and Europe, while in Asia 504.5 mha arable land stored 153.3 GtC by biochar. Also, it was estimated that in Central America and Oceania, 36.5 to 45.6 mha arable land stored 10.9 to 13.9 GtC biochar carbon. Biochar of 1.65 GtC y−1 amendment to the soil is beneficial to minimize 19% of CO2 emissions from agriculture land which was noticed in rice yield cropping system (Mehmood et al. 2020). Agricultural and grassland soils have the feasible economic potential of 1.5 to 2.6 Gt CO2eq per year (at a price up to 100 USD$ per t CO2eq), while biochar amendment is more feasible for 2.6 Gt CO2eq per year and takes a long time to emit CO2 (Vetter et al. 2022).

3.7.1 Biochar for greenhouse gas emission mitigation from crop land

The application of biochar for mitigating anthropogenic GHGs emissions from agriculture soil was presented in Fig. 6 (Li et al. 2023; Liu et al. 2011; Zheng et al. 2016; Zhou et al. 2019a, b). The emissions of GHGs are due to the effective soil properties, pH, C/N and H/C (Zhang et al. 2012). Biochar application has been found extremely efficient for the mitigation of GHGs as NH4+, CO2, CH4, H2S, TN and NO2. In some studies, N2O emissions are observed as being sensitive to feedstocks used for biochar, pyrolysis conditions, soil pH and texture, biochar properties and application rate (Zhang et al. 2010).

Fig. 6
figure 6

Greenhouse gas (GHG) mitigation by biochar derived from food waste feedstocks in crop production

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Many studies examined long term effects of biochar application on agriculture soil CO2 emission including variation in microbial community changes in physical habitat structure, physical and chemical protection of intrinsic soil organic matter (Yang et al. 2017). Certain studies suggested that lower fraction of biochar amendment minimizes emission of CO2 from agriculture field but such effect can be degraded by the crop canopies (Zhang et al. 2012). Thus, when biochars appear to pose a nominal risk to exacerbating soil CO2 emissions in the long-term practice, more studies are needed to ascertain whether CO2 responses to food waste biochar amendment are suitable to predict CO2 responses in the field for long-term CO2 emissions. Additionally, most of the studies have found that biochar amendments do not affect or slightly decrease N2O emissions, but a few studies reported that biochar amendment increases NO2 emissions. Zhang et al. (2010) reported, in their study, that the biochar application rate will reduce N2O emission by 54 ± 3% at the lab scale and by 28 ± 16% at the field scale. The higher variability of the field scale estimate indicates that a lower fraction of biochar application rate is required in cropping systems, which is beneficial for reducing GHGs compared to higher rate of biochar application and controlled conditions with a variable climatic condition.

3.8 Limitations of biochar use

Numerous negative aspects of biochar as an amendment were also reported due to climatic conditions, soil type, crop type and dosage of biochar (Bista et al. 2019; Mukherjee et al. 2011; Warnock et al. 2007). The authors also classified some negative impacts of biochar on crop yields and pointed out the impact of biochar applications on increasing gaseous emissions, and lower nutrient uptake. Amendment of biochar in agriculture was found harmful to microorganisms to some extent due to the presence of some organic products like phenolics and polyphenolics in biochar (Bista et al. 2019). Warnock et al. (2007) and Ennis et al. (2012) reported that mycorrhizae and their total microbial biomass declined with an increase of some metal release after applying higher fraction of biochar. It is not convincing to conclude that biochar application has negative impacts on soil biota as it has high positive influence. For example, George et al. (2012) reported that hydrochar could be beneficial for arbuscular mycorrhizae but may hinder plant growth. Several properties of biochar as chlorine (Cl) or sodium (Na) salt are likely to be responsible for the negative effects on soil biota (Domene et al. 2015) but most of the properties promote positively on soil quality improvement. Moreover, detailed research is required to analyze the long-term effects of biochar application on agriculture soil in order to overcome these critical issues.

3.9 Future research directions

This study emphasizes advanced studies on potential impact of biochar produced from food waste on soil water retention capacity and loss of nutrients by leaching through irrigation. Additionally, it is necessary to explore the influence of different fractions of food waste biochar application on emissions of GHG from different types of degraded soils. This study encourages researchers to focus on multi functions of biochar produced from solitary and blended food waste that will assign to apply in environmental sectors. Unpredictable climate change impacts on growing crops are the most challenging aspect for food security stress, and thus this study supports further research into engineer biochar as an amendment for desert sand and arid land.

4 Conclusion

This review summarized detailed findings on the promising benefits of food waste valorization for a valuable product that could be commercially appliable in agriculture and environmental pollution remediation. This study addressed a finest approach for food waste valorization to biochar by pyrolysis and analyzed in detail the impact of pyrolysis temperature on various properties such as CEC, ζ-potential, BET surface area, etc., which is inadequate in reported studies. This study explained in detail the constructive role of food waste biochar application as an amendment in agriculture which will encourage the researchers to pick appropriate food waste type, pyrolysis temperature for biochar production, crop and soil type and biochar fraction for larger scale agriculture production. This study emphasized that in previous studies, there was a lack of significance of survey covering the biochar impact on soil (a) microbial activity, (b) water retention and (c) nutrients uptake. Considering a wide range of environmental challenges for soil pollution, water pollution and climate changes, this study expanded how food waste biochar is impactful for removing different types of pollutants from soil and water and mitigate GHGs. This study also analyzed and reported the mechanism of biochar, soil, microbes and plant interaction in agriculture land for the transparency of key research targets on information gaps of biochar amendment. This study scoped significant reduction of expensive chemical fertilizers uses which are also toxic for environment by amending biochar. This study also encouraged the farmer community and stakeholders in terms of how they can get maximum profit from their limited resources by adopting ecofriendly pyrolysis technique to recycle food waste to an economical product “biochar”.