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2. What are the pros and cons of bioenergy?

The Executive Summary of the IAASTD Synthesis Report states:

Figure SR-BE1. From biomass to energy consumption

Themes

The Synthesis Report looked at eight AKST-related [related to Agricultural Knowledge Science and Technology] themes of critical interest to meeting IAASTD goals: bioenergy, biotechnology, climate change, human health; NRM [Natural Resource Management]; trade and markets; traditional and local knowledge and community-based innovation; and women in agriculture.

Bioenergy

2.1 Rising costs of fossil fuels, energy security concerns, increased awareness of climate change, and potentially positive effects for economic development have led to considerable public attention to bioenergy. Bioenergy includes traditional bioenergy, biomass to produce electricity, light and heat and first and next generation liquid biofuels. The economics and the positive and negative social and environmental externalities differ widely, depending on source of biomass, type of conversion technology and local circumstances.

2.2 Primarily due to a lack of affordable alternatives, millions of people in developing countries depend on traditional bioenergy (e.g. wood fuels) for their cooking and heating needs, especially in sub-Saharan Africa and South Asia. This reliance on traditional bioenergy can pose considerable environmental, health, economic and social challenges. New efforts are needed to improve traditional bioenergy and accelerate the transition to more sustainable forms of energy.

2.3 First generation biofuels consist predominantly of bioethanol and biodiesel produced from agricultural crops (e.g. maize, sugar cane). Production has been growing fast in recent years, primarily due to biofuel support policies since they are cost competitive only under particularly favorable circumstances. The diversion of agricultural crops to fuel can raise food prices and reduce our ability to alleviate hunger throughout the world. The negative social effects risk being exacerbated in cases where small-scale farmers are marginalized or displaced from their land.

From an environmental perspective, there is considerable variation, uncertainty and debate over the net energy balance and level of GHG emissions. In the long term, effects on food prices may be reduced, but environmental effects caused by land and water requirements of large-scale increases of first generation biofuels production are likely to persist and will need to be addressed.

2.4 Next generation biofuels such as cellulosic ethanol and biomass-to-liquids technologies allow conversion into biofuels of more abundant and cheaper feedstocks than first generation. This could potentially reduce agricultural land requirements per unit of energy produced and improve lifecycle GHG emissions, potentially mitigating the environmental pressures from first generation biofuels. However, next generation biofuels technologies are not yet commercially proven and environmental and social effects are still uncertain. For example, the use of feedstock and farm residues can compete with the need to maintain organic matter in sustainable agroecosystems.

2.5 Bioelectricity and bioheat are important forms of renewable energy that are usually more efficient and produce less GHG emissions than liquid biofuels and fossil fuels. Digesters, gasifiers and direct combustion devices can be successfully employed in certain settings, e.g., off-grid areas.

2.6 There is potential for expanding these applications but AKST is needed to reduce costs and improve operational reliability. For all forms of bioenergy, decision makers should carefully weigh full social, environmental and economic costs against realistically achievable benefits and other sustainable energy options.

Source & ©: IAASTD  Executive Summary of the Synthesis Report (April 2008), p.12-13