Food and Energy Production from Biomass in an Integrated Farming System

Abstract

This chapter describes experiences in a small farm in the Colombian foothills, in which the aim was to demonstrate – and at the same time to research – the major components of the strategy that should underpin all future farming systems: namely the need to “decarbonize” the system, by reducing emissions of greenhouse gases, generating electricity locally from natural resources, making maximum use of solar energy and ensuring there is no conflict between use of available resources for both food and fuel production. The inevitable decline in the production of oil (peak oil), which will have negative effects on all features of contemporary lifestyles, is viewed from the positive standpoint of the opportunities that will be created for more sustainable farming systems when solar energy, via the production of biomass, will be the basis of the required needs for food, feed and fuel energy.

It is argued that in such a scenario, small scale integrated family farms, will have comparative advantages – economic, social and environmental – in a world in the decline phase of the oil age and increasing dependence on solar energy. Transport is the major end user of fossil fuel, thus as the supply of this resource diminishes and the price increases, there will be advantages in decentralization and localization of both production and processing of the immediate products of photosynthesis which are of low bulk density and therefore expensive to transport. An analysis of the alternative technologies for production of fuel energy from biomass, as a component of a farming system, leads to the conclusion that gasification is the most appropriate route. The advantages of this process are that: the feedstock is the fibrous parts of plants which are not viable sources of food or feed. The energy used to drive the process is derived from the combustion of the feedstock and there is minimal input of external sources of energy, (mainly for the construction of the gasifier and associated machinery). The products of gasification are a combustible gas and a carbon-rich residue (biochar). The gas can be used to drive an internal combustion engine linked to an alternator producing electricity; while the biochar when returned to the soil can be a sink for sequestering carbon and a means of improving soil fertility.

The role of livestock in the farming system is emphasized as the means of optimizing the use of highly productive perennial crops such as sugar cane and multi-purpose trees. Sugar cane is easily separated into energy-rich juice which can replace cereal grains in feeding of pigs and residual bagasse which is one of the feed-stocks of the gasifier. Forage trees are the natural feed resources for goats which selectively consume the leaves, leaving the fibrous stems as another feedstock for gasification. Sugar cane juice contains no fibre and almost no protein which creates opportunities for use of vegetative sources of protein such as the foliage of perennial plants, among which Taro (Colocacia esculenta) and New Cocoyam (Xanthosoma sagittifolium) have been found to have many advantages. It is concluded that integrated, small scale, farming systems based around multi-purpose crops and livestock, can provide food, feed and fuel energy with no conflict among these end uses. Gasification of fibrous crop residues produces electricity and a soil conditioner (biochar) that is also a sink for sequestration of atmospheric carbon. Bio-digestion of all liquid wastes produces a gaseous fuel for cooking with alternative use as a complement to the gaseous fuel from the gasifier. The system delivers real benefits for the environment as a negative carbon footprint through carbon sequestration and improvements in soil fertility.