Energy Resource from Agriculture: Prospects and Problems

Abstract

This paper examines the links between agriculture and energy. It highlights the role of agriculture as an energy, food and industrial raw materials producer. This function implies greater agricultural productivity and higher levels of energy sustainability through the production of CO₂-neutral bioenergy. Biomass was the main source of energy until the early 20th century. However, biomass energy was relegated and ignored by policy makers and energy planners alike during the past few decades. Biomass is defined as all organic matter except fossil fuels. Biomass comes in many forms: wood, annual crops, crop residues, animal manure, marine plants, algae, and others. Biomass may be burned directly to produce heat or converted to more useful solid, liquid or gaseous forms. Then it can be stored and subsequently used for fuel. Before energy can be used for end-use activities, it often has to be converted from its primary (raw) form into a form that is more convenient for transport and use. The processes of conversion of biomass to fuel are: 1. Production of Fuelwood still remain drying and resizing by cutting and splitting into sizes that are easy to transport. Fuelwood includes "wood in the rough" in small pieces, chips, pellets and/or powder (sawdust) derived from forests and isolated trees, as well as wood by-products from the wood industry and from wasted wood products. 2. Charcoal is produced in kilns by a process called pyrolysis, i.e. breaking down the chemical structure of wood under high temperature in the absence of air. 3. Briquetting or densification is process of compacting biomass material, and depending on the nature of the material, the applied pressure, and the speed of densification, additional binders may be needed to bind the material. 4. Gasification is the process in which solid biomass fuels (e.g. wood, charcoal) are broken down by the use of heat to produce a combustible gas, known as producer gas. 5. Ethanol can be produced by the fermentation of glucose derived from sugar-bearing plants (like sugar-cane) or starchy materials (like cassava) after hydrolysis. 6. Biodiesel is produced through transesterification process. This involves vegetable or animal fats and oils being reacted with short-chain alcohols (typically methanol or ethanol) in the presence of catalyst, producing biodiesel and glycerol. A transition to more sustainable rural energy systems is urgent, and agriculture could make an important contribution in this respect. A more extensive use of bioenergy will lead to considerable benefits to the global environment and to the development of local infrastructure, but the potential conflicts with food production and impacts of land use change must be followed closely. FAO is currently strengthening its bioenergy programme with the aim of contributing to a partial substitution of fossil fuels with biofuels