Keywords

1 Introduction

The manufacturing process of most conventional building materials poses various environmental issues, and the brick and block manufacturing process is no exception. To name a few of these issues, when manufacturing burnt clay bricks there is depletion of fertile topsoil and emissions of CO2 to the atmosphere [1]. Conventional bricks are produced from clay with high-temperature kiln firing or from ordinary Portland cement concrete, and thus contain high embodied energy and have a large carbon footprint [2]. To protect the clay resource and with the vision of developing ecofriendly building materials, certain cities in China have banned the use of clay bricks [3]. Brick manufacturing with higher resource efficiency and less carbon footprint is the priority. Industrial byproducts such as fly ash/pond ash are alternatives in brick and block manufacturing process. Fly ash is a fine industrial waste byproduct often found after coal combustion for power generation.

There are research studies of using byproducts in the brick manufacturing process. Cicek and Tanriverdi [4] conducted research on using fly ash from thermal coal power plants for brick manufacturing in Turkey. Several research studies have used various percentages of fly ash in the process of manufacturing bricks; for example, Wang et al. [5] introduced a technology to use up to 50% of fly ash in brick manufacturing. Using pond ash as an alternative to sand is another viable alternative in the block manufacturing process [6]. Similarly, there are many research studies on using fly ash as a replacement material in both brick and block manufacturing [7, 8].

Although research has been conducted on ecofriendly brick/blocks using industrial waste, the commercial production of such bricks is still very limited [2]. Slow acceptance of waste materials-based bricks by industry and the public is one of the challenges faced when commercializing these innovative products [2]. One of the main reasons for this limited use in the commercial space is economic considerations, because incorporating these byproducts is deemed to be costlier compared with conventional materials.

Most research studies rarely discuss the economic aspects from initial investment, construction cost, operational cost and recycling or reuse opportunities. Although these studies used industrial waste, the environmental impacts were rarely quantified using valid parameters. Therefore, this research study conducted a whole of life-cycle cost analysis of Nu-Rock blocks.

1.1 Nu-Rock Blocks: Properties and Manufacturing Process

In Australia, 54% of electricity is generated from coal combustion [9]. Thermal coal power plants generate fly ash and bottom ash, and these are mixed with water, resulting in a slurry that is carried to ash ponds [10]. When the Port Augusta power plant closed, it created a huge pile of pond ash covering hectares of land, giving rise to many environmental and social issues [11]. Nu-Rock technology uses this pond ash to manufacture a range of building materials.

Nu-Rock Technology Pty. Ltd. is a privately owned company providing solutions for environmental and economic issues related to the growing stockpiles of industrial byproducts occurring worldwide. Nu-Rock produces a range of products, including common or rendered bricks and blocks, masonry bricks, blocks, pipes, pavers, tiles, sheeted products and any other shaped building products [12]. Our study focused on the manufacturing of three types of Nu-Rock blocks, namely Mighty block (90 × 245 × 470 mm), 200 series (190 × 190 × 390 mm), and 100 series (90 × 190 × 390 mm). The Nu-Rock Technology has a Proprietary IP. The recycling process usually converts 100% of the pond ash in abandoned power plants into building blocks and brick products. The product has undergone rigorous testing including (but not limited) AS3700D Flexural strength, AS1191 Acoustic fire and AS1530.4 Fire resistance.

The first step in the Nu-Rock block manufacturing process is called Nu-creeting, which prevents dust generation and builds “modules” to process the pond ash. Nu-Rock can process 250,000 tonnes of ash per annum and manufacture the equivalent of up to 330,000 tonnes of traditional building materials using the pond ash as an input [13]. Each module in Nu-Rock can process approximately 0.25 million tonnes of ash per annum and each module can produce a specific type of product. Nu-Rock Blocks require only 3% of the embodied energy required to produce traditional concrete blocks and the Nu-Rock manufacturing process produces zero waste [14]. According to Tam et al. [11], there are great benefits in using this technology to remediate ash ponds.

2 Methods

The primary objective of this research study was to conduct a life-cycle cost analysis of the entire Nu-Rock block manufacturing process: block manufacturing, transportation, operational stage of the building and the demolition. However, here we present the results for initial stages up to construction.

2.1 Scope of the Analysis

The scope of the analysis was the entire process of blocks from cradle to cradle, calculated in four stages:

  • Stage 1—Initial stage including setting up the plant.

  • Stage 2—Raw material extraction, manufacturing, transportation to construction site.

  • Stage 3—Construction, operation, and maintenance.

  • Stage 4—Demolition/re-use phase.

The data are for stages 1 and 2 up to construction. The calculations included sensible assumptions and limitations, which are given with the relevant calculations.

2.2 Life-Cycle Cost

Key parameters of a life-cycle analysis are determined to a large extent by its purpose and objectives [15]. The main parameters of this project included costs, period of analysis, method of economic evaluation, extent of environmental input and sensitivity analysis. Each of these parameters is discussed in detail.

Costs included those incurred by Nu-Rock Technology Pty Ltd and by the end-users. The life-cycle cost calculation followed ISO15686-5:2017: Building and construction assets—service life planning—Part 5: Life cycle costing” as a guideline. When a decision required including any cost or income in the analysis, the ISO standard was followed. However, additional notes illustrate if any exception was made. All the assumptions (if any) relevant to each calculation are given with it. This project selected an analysis period of 60 years to reflect the anticipated total lifespan of Nu-Rock Technology Pty Ltd.

All costs incurred within the life cycle must be captured and discounted into present day values to calculate the life-cycle cost. Net present value (NPV) was the economic evaluation method used for life-cycle cost calculation, as shown in Eq. 1 (adapted from Dell'Isola and Kirk [15])..

$${N}{P}{V}\left( {i,N} \right) = \sum_{t = 0}^N {\frac{R_t }{{\left( {1 + i} \right)^t }}}$$
(1)

In Eq. 1, i denotes the discount rate; t denotes the time of cash flow; Rt denotes the net cash flow, and N is the total number of periods. The discount rate considers the time value of money and the associated risk. The return on equity (RoE) of Nu-Rock Technology Pty Ltd was used as the discounting rate in the life-cycle cost calculation to reflect the capital used by the company (RoE was provided by Nu-Rock).

2.2.1 Life-Cycle Cost Analysis

The initial investment cost for Nu-Rock was AUD12,000,000, which included land cost, specialized design costs, construction cost, cost for initial approvals, electricity connection charges, water connection charge, cost of machinery, cost of specialized equipment and other professional fees. The site establishment cost of AUD200,000 was not included in the investment cost. Therefore, the total initial investment was AUD12,200,000 including site establishment.

Life- cycle cost calculations were based on the following sensible assumptions.

  • Transportation costs included loading and unloading and bulk discounts for blocks were not considered. Investment costs provided by Nu-Rock were for the Mt. Piper plant.

  • On-site labor costs include one site manager, four factory staff, including two for lift drivers and accounts manager. Salary and associated costs were provided by Nu-Rock.

  • Repair and maintenance costs were 5% of the plant costs. The initial investment cost of AUD12,000,000.00 was taken as the plant costs.

  • Distribution cost included AUD30 per tonne as provided by Nu-Rock.

  • Operational costs included other miscellaneous operations and energy costs. The cost per kWh was considered to be 66 cents/kWh.

Table 1 summarizes the life-cycle costs for Nu-Rock during the raw material extraction and manufacturing stage. The life-cycle cost for the 60-year period at 15% discount rate per tonne of blocks was AUD321.

Table 1 Life-cycle costs for Nu-Rock during the raw material extraction and manufacturing stage
Full size table

The next phase was the construction, operations and maintenance stage. This cost calculation included a wall construction using Nu-Rock blocks. “Wall” was assumed as a face brick without any finishing. The size and further details of the three types of Nu-Rock block are given in Table 2.

Table 2 Construction cost for Nu-Rock block types
Full size table

Stages 3 and 4 are not discussed here but are expected to derive savings by using Nu-Rock.

The selling price of a Nu-Rock block varies between AUD 1.50 and 2.40 which is within the range of common bricks. When setting up the factory Nu-Rock incurred an initial cost of AUD12,200,000. The cost attributed during material extraction was AUD48 per tonne of Nu-Roc blocks (refer to Table 1). During this phase Nu-Rock blocks absorb industrial byproducts such as waste from coal-fired power stations, steel mills, non-ferrous smelters and alumina smelters. This is a non-quantifiable benefit of using Nu-Rock blocks. According to Tam et al., the Nu-Rock manufacturing plant provides almost AUD20 million worth of jobs [11], which is a significant social benefit.

3 Conclusions

The life-cycle cost impacts of Nu-Rock blocks for the first two stages of the manufacturing process, starting from setting up the factory up to the actual construction, were calculated. Nu-Rock technology uses pond ash to manufacture blocks. Ash ponds in discontinued power plants pose serious environmental and social threats. According to our life-cycle calculations, the cost of setting up the factory was ≈ AUD12.2 million. The life-cycle cost for the 60-year period at 15% discount rate per tonne of blocks was AUD321. However, it is interesting to note that the cost of Nu-Rock blocks was within the range of conventional bricks. Although there are many research studies of environmentally friendly materials using industrial byproducts, the commercialization of these products is very slow. It is necessary to conduct similar economic and environmental impact analyses of these products to ensure end-users of their importance. Although this research study was limited to the first two stages, we are planning to extend the study to include stage 3 and 4 in the life-cycle cost calculation.