Box 1: Other types of biomass for heat, power and transport

Biomass for heat and power

A range of biomass resources are used to generate electricity and heat through combustion. Sources include various forms of waste, such as residues from agro- industries, post-harvest residues left on the fields, animal manure, wood wastes from forestry and industry, residues from food and paper industries, municipal solid wastes, sewage sludge and biogas from the digestion of agricultural and other organic wastes. Dedicated energy crops, such as short-rotation perennials (eucalyptus, poplar, willow) and grasses (miscanthus and switchgrass), are also used.

Several processes can be used for power generation. Most biomass-derived electricity is produced using a steam- cycle process: biomass is burned in a boiler to generate high-pressure steam that flows over a series of aerodynamic blades causing a turbine to rotate, which in response turns a connected electric generator to produce electricity. Compacted forms of biomass such as wood pellets and briquettes can also be used for combustion, and biomass can also be burned with coal in the boiler of a conventional power plant to yield steam and electricity. The latter is currently the most cost-efficient method for incorporating renewable technology into conventional power production because much of the existing power plant infrastructure can be used without major modifications

Biogas for heat, power and transport

Anaerobic digestion

Biogas can be created through the anaerobic digestion of food or animal waste by bacteria in an oxygen-starved environment. The resulting biogas contains a high volume of methane along with carbon dioxide, which can be used for heating or for electricity generation in a modified internal combustion engine.

Methane is a greenhouse gas that has a global-warming potential that is 22–24 times more powerful than that of carbon dioxide. By trapping and utilizing the methane, its greenhouse gas impacts are avoided. In addition, heat generated during the biodigestion process kills the pathogens present in manure, and the material left at the end of the process provides a valuable fertilizer.


Through the process of gasification, solid biomass can be converted into a fuel gas or biogas. Biomass gasifiers operate by heating biomass in a low-oxygen, high- temperature environment that breaks it down to release a flammable, energy-rich synthesis gas or “syngas”. This gas can be burned in a conventional boiler, or used instead of natural gas in a gas turbine to turn electric generators. Biogas formed through gasification can be filtered to remove unwanted chemical compounds and can be used in efficient “combined- cycle” power-generation systems that combine steam and gas turbines to generate electricity.

Biogas for transport

Untreated biogas is unsuitable as a transport fuel owing to its low methane content (60–70 percent) and high concentration of contaminants. However, it can be treated to remove carbon dioxide, water and corrosive hydrogen sulphide and to enhance its methane content (to over 95 percent). When compressed, treated biogas has properities similar to those of compressed natural gas, making it suitable for use in transport.

Source: FAO, The State of Food and Agriculture, Biofuels: Prospects, Risks and Opportunities (2008) , Chapter 2, Section Liquid biofuels for transport, p.12

Related publication:
Biofuels homeLiquid Biofuels for Transport Prospects, risks and opportunities
Other Figures & Tables on this publication:

TABLE 1: Biofuel production by country, 2007

TABLE 2: Biofuel yields for different feedstocks and countries

TABLE 3: Hypothetical potential for ethanol from principal cereal and sugar crops

TABLE 4: Voluntary and mandatory bioenergy targets for transport fuels in G8+5 countries

TABLE 5: Applied tariffs on ethanol in selected countries

TABLE 6: Total support estimates for biofuels in selected OECD economies in 2006

TABLE 7: Approximate average and variable rates of support per litre of biofuel in selected OECD economies

TABLE 8: Energy demand by source and sector: reference scenario

TABLE 9: Land requirements for biofuel production

TABLE 10: Water requirements for biofuel crops

TABLE 11: Import bills of total food and major food commodities for 2007 and their percentage increase over 2006

TABLE 12: Net importers of petroleum products and major cereals, ranked by prevalence of undernourishment

TABLE 13: Share of net staple food-seller households among urban, rural and total households

Box 1: Other types of biomass for heat, power and transport

Box 2: Biotechnology applications for biofuels

Box 3: Biofuel policies in Brazil

Box 4: Biofuel policies in the United States of America

Box 5: Biofuel policies in the European Union

Box 6: Main sources of uncertainty for biofuel projections

Box 7: Biofuels and the World Trade Organization

Box 8: Biofuels and preferential trade initiatives

Box 9: The Global Bioenergy Partnership

Box 10: Biofuels and the United Nations Framework Convention on Climate Change

Box 11: Jatropha – a “miracle” crop?

Box 12: Agricultural growth and poverty reduction

Box 13: Cotton in the Sahel

Box 14: Biofuel crops and the land issue in the United Republic of Tanzania

Figure 1: World primary energy demand by source, 2005

Figure 2: Total primary energy demand by source and region, 2005

Figure 3: Trends in consumption of transport biofuels

Figure 4: Biofuels – from feedstock to end use

Figure 5: Uses of biomass for energy

Figure 6: Conversion of agricultural feedstocks into liquid biofuels

Figure 7: Estimated ranges of fossil energy balances of selected fuel types

Figure 8: Support provided at different points in the biofuel supply chain

Figure 9: Biofuel production costs in selected countries, 2004 and 2007

Figure 10: Breakeven prices for crude oil and selected feedstocks in 2005

Figure 11: Breakeven prices for maize and crude oil in the United States of America

Figure 12: Breakeven prices for maize and crude oil with and without subsidies

Figure 13: Maize and crude oil breakeven prices and observed prices, 2003–08

Figure 14: Price relationships between crude oil and other biofuel feedstocks, 2003-08

Figure 15: Food commodity price trends 1971–2007, with projections to 2017

Figure 16: Global ethanol production, trade and prices, with projections to 2017

Figure 17: Major ethanol producers, with projections to 2017

Figure 18: Global biodiesel production, trade and prices, with projections to 2017

Figure 19: Major biodiesel producers, with projections to 2017

Figure 20: Total impact of removing trade-distorting biofuel policies for ethanol, 2013–17 average

Figure 21: Total impact of removing trade-distorting biofuel policies for biodiesel, 2013–17 average

Figure 22: Life-cycle analysis for greenhouse gas balances

Figure 23: Reductions in greenhouse gas emissions of selected biofuels relative to fossil fuels

Figure 24: Potential for cropland expansion

Figure 25: Potential for yield increase for selected biofuel feedstock crops

Figure 26: Potential for irrigated area expansion

Figure 27: Agricultural trade balance of least-developed countries

Figure 28: Distribution of poor net buyers and sellers of staple foods1

Figure 29: Average welfare gain/loss from a 10 percent increase in the price of the main staple, by income (expenditure) quintile for rural and urban households