If biomass energy is to contribute meaningfully to climate mitigation—without posing unacceptable risks to food security—a multi-pronged approach is necessary. Bioenergy programs must be pursued on scales both large and small, and in the developed and developing worlds alike.
In Round Two, I focused on small-scale bioenergy projects in the developing world—on the contributions they can make to development and the carbon emissions they can prevent. My Roundtable colleagues, in their own Round Two essays, criticized this approach. José R. Moreira argued, as he had in Round One, in favor of large-scale bioenergy systems, biofuels in particular. Roberto Bissio, who is highly skeptical of many forms of bioenergy, criticized small bioenergy projects because he feels they deflect attention from the need for reduced emissions in countries belonging to the Organisation for Economic Co-Operation and Development.
I acknowledge that bioenergy projects must be carried out on a large scale to achieve significant short-term cuts in emissions. But short-term cuts in greenhouse-gas emissions aren't the only goal. Long-term emissions count as well, as do food security and development. Small-scale bioenergy technologies can contribute along all of these dimensions. And of course it is true that short-term efforts to reduce emissions must focus on nations where emissions are now highest (mostly developed countries, but a few developing ones as well). But one must also remember that developing countries are now putting in place infrastructure that will supply their energy for a long time. It is important that they adopt sustainable energy strategies that do not lock them into using fossil fuels. Small-scale bioenergy projects are one such strategy.
Biomass technologies, whether large-scale or small-scale, should be assessed on their individual merits and pursued in the places where they are appropriate. Large projects are appropriate for countries where land can be devoted to producing biomass feedstock without harming food production, biodiversity, and water supply. These projects may include, among other things, biofuels and multi-megawatt biomass power systems. But in rural areas where poor energy access hinders development, small-scale bioenergy systems will often be appropriate. As I discussed in Round Two, efficient biomass cookstoves and biogas systems for cooking could help meet the energy needs of the 2.7 billion people who lack access to clean cooking facilities. And regions rich in biomass but poor in fossil fuels might be able to use small-scale biomass energy systems to produce liquid transportation fuels—and also, as a byproduct, substantial quantities of cost-competitive liquid petroleum gas for cooking. Such systems could integrate carbon capture and storage, thus contributing to climate mitigation.
No simple solutions are available for mitigating climate change and meeting the world's increasing need for food and energy. All nations, whether developed or developing, must explore various avenues for climate mitigation, whether large-scale or small-scale. In any event, bioenergy technologies, along with carbon capture and storage, will be an integral component of future strategies to meet energy needs and keep global warming within the acceptable range of 1.5 to 2 degrees.