Climate, food, and biomass energy

Bioenergy, because of its potential to mitigate climate change and contribute to energy security and rural development, has attracted increased attention in recent years. It is a highly versatile energy source whose most common applications are heat energy for cooking and biofuels for transportation, but it can also encompass electricity. Biofuels such as ethanol and biodiesel can be produced from crops like sugarcane or corn; biomass energy can be derived from (usually woody) feedstock through processes running the gamut from simple combustion in a cookstove to biochemical conversion.

Another advantage of bioenergy is that, compared to fossil fuels, it is distributed equitably across the world and is accessible to communities everywhere—including poor people in rural areas, who tend to be very dependent on traditional biomass-based energy for cooking and heating and even for mechanical applications such as lift irrigation. Traditional biomass is often inefficient, harmful to the environment, and associated with low quality of life, but several modern bioenergy technologies have emerged that can, in an environmentally sustainable way, meet rural people's energy needs. These technologies include efficient biomass cookstoves, biogas systems for cooking and for decentralized power generation, gasification of woody biomass, and biofuels for transportation.

Meanwhile, bioenergy technologies are increasingly being recognized for their potential to mitigate climate change. According to the 2012 Global Energy Assessment, bioenergy is essential if global temperature increases are to be limited to between 1.5 and 2 degrees Celsius. In many applications, bioenergy may be able to displace fossil fuels, as with biofuels for transportation. But another critical approach is to combine biomass energy with carbon capture and storage. This technology involves growing crops that absorb carbon dioxide, burning them to produce energy, and capturing and storing the carbon that results from the combustion. Capture and storage of carbon dioxide emissions from bioenergy conversion has the potential to generate negative emissions—to remove carbon from the atmosphere.

But the technology's potential as a mitigation option is still uncertain due to constraints on carbon capture and storage itself, and due to the difficulties associated with producing supplies of biomass. Biomass energy combined with carbon capture and storage must be deployed on a large scale if it is to have a significant impact on global emissions of greenhouse gases; this is true of biofuels as well. Large-scale deployment of these two technologies implies sustained, large-scale production of bioenergy feedstock, and this carries potential implications for food security.

Potential and contention. The food-security implications differ for the two technologies, not least in terms of their feedstock. For biomass energy combined with capture and storage, woody (or ligneous) feedstock is generally required. This can be sourced from tree plantations, but if either croplands or forests were used on a commercial scale for woody biomass production, food security and biodiversity could be adversely affected. However, if sustainable tree plantations were established on degraded land or fallow crop lands, implications for food security would be minimal. And using residues from forests or croplands would have no implications for food security.

Feedstock for biofuels, meanwhile, can be thought of as belonging to two generations: first-generation crops like palm oil (which can be used to produce biodiesel) and sugarcane (which can be used to make ethanol); and next-generation sources such as microalgae (used to produce biodiesel) and woody biomass, tall grasses, and agricultural residues (used for ethanol). First-generation biofuels pose the greater risks to food security, and imply negative environmental effects like reduced biodiversity and increased water usage. These negative effects are likely to be particularly acute in the developing world, where, due to low production costs, the bulk of future biofuel production is likely to occur. So even though biofuels can promote rural development, create rural jobs, and reclaim degraded land, they have become highly contentious.

Nonetheless, technology for converting second-generation feedstock into biofuels holds out substantial promise for avoiding many of the challenges associated with first-generation feedstock. Agricultural or forest residues and short-rotation woody crops could be sourced from marginal or degraded lands. This would be unlikely to have significant implications for food security, livestock feed, and fiber production. Moreover, new biofuel technologies can be expected to provide net benefits in emissions of greenhouse gases.

Taking all this into account, it is difficult to generalize about bioenergy's ability to meet energy needs and mitigate climate change while avoiding adverse effects on food production, biodiversity, and so forth. The impacts of bioenergy use depend on the technology used (biofuel production versus other forms of biomass energy), the feedstock used (forest or crop residues versus food grains, for example), and the scale of production.

Over the last three decades, the amount of land devoted to food crops has increased at a very modest rate, but worldwide food production has expanded significantly. The UN Food and Agriculture Organization expects that patterns will be similar over the coming decades: Food demand through 2050 will increase at a rate of 1.1 percent a year, but this increased demand will mainly be met through productivity gains, with only a small expansion in cropland required. If productivity gains come in below expectations, there are large amounts of land available that could be used for crop expansion. Availability of land is not a major obstacle to the expansion of bioenergy production.

But climate change may have a negative impact on biomass productivity (that is, on production of agricultural crops and bioenergy feedstock) due both to higher temperatures and to reduced water availability. Some argue that the effects of these changes could be especially severe in the developing world. Today's temperatures in tropical areas, according to this argument, are very near the optimum for growing tropical crops, and higher temperatures would seriously harm productivity. Temperate regions, on the other hand, might actually experience higher yields along with higher temperatures. Since much of the developing world is located in the tropics, the effect of higher temperatures would be especially severe in poorer countries. But one must tread carefully here. If average temperatures increase 2 degrees Celsius or more, it is certain that the environment will change in many ways—but predicting with accuracy how specific regions will be affected is very difficult. It is not so easy to conclude that decreases in agricultural production would be most pronounced in developing countries.

Nevertheless, if one assumes that higher average temperatures around the world will affect biomass production negatively, the question then becomes to what extent bioenergy can mitigate climate change. Bioenergy can be produced in good ways or bad ways. But if environmentally friendly technologies are used and proper policies are in place, evidence suggests that bioenergy can significantly reduce emissions of greenhouse gases and meaningfully mitigate the negative impacts of climate change.

My colleague Sergio Pacca and I have calculated that 70 million hectares of sugarcane planted worldwide could—by 2030, when the world car fleet will amount to 1.6 billion vehicles—replace all gasoline and diesel used in cars and trucks (as long as the vehicles are of the plug-in hybrid variety). Sugarcane could also generate the electricity that these hybrid vehicles would consume. A huge amount of carbon dioxide emissions could be avoided this way.

Some experts believe that, without heavy reliance on bioenergy, it will be impossible to keep planetary warming below 2 degrees, but that if bioenergy is used properly, and other mitigation options are also pursued, the 2-degree threshold might not be crossed (in which case climate change would cause no serious problems for food supply). Several studies have determined that, if fossil fuel use does not decline quickly enough to limit warming to 2 degrees or less, it may be necessary to combine bioenergy with carbon capture and storage in order to bring down concentrations of greenhouse gases. This might mean that greenhouse gases would be removed from the atmosphere through the growth of crops, with the crops then burned to produce energy and the resulting carbon captured and stored. But biofuels could be an important part of this approach as well.

To begin with, biofuels made from certain feedstocks—mainly sugarcane, but also corn, animal grease, and properly planted palm oil—produce carbon emissions lower than those for gasoline and diesel over their full life cycle. Bringing carbon capture and storage into the picture might in some cases result in negative emissions. This may be the case with sugar fermentation, a process necessary for producing ethanol from sugar, starch, or even cellulosic material. During fermentation, glucose is essentially split into two products: ethanol and carbon dioxide. The carbon dioxide is typically vented into the atmosphere. But with no further treatment, this very pure carbon dioxide stream could be sent underground into saline aquifers or empty gas or oil reservoirs. This would be one of the least expensive ways to carry out carbon capture and storage, as virtually the only action required is storage. This technology is being pioneered in Decatur, Illinois, and another project in Brazil has received approval from the Global Environmental Facility. Combining biofuels with carbon capture and storage is one of the very few technologies that can remove carbon from the atmosphere and bring carbon concentrations down.

But how much climate mitigation could already have been achieved if nations had begun pursuing bioenergy on a large scale as long ago as 1980? (At that time, examples of good bioenergy projects already existed, and it was around then that publics began to learn about the possibility of climate change.) My calculations suggest that by 2015 it would have been possible, through expansion of sugarcane-based biofuels alone, to cut annual carbon emissions by nearly 9 percent. Nothing can be done today about decisions made in 1980. But in the years to come, I believe that bioenergy must be a major strategy if temperatures are to be prevented from reaching truly dangerous levels.

In May of this year, the measurement station atop the Mauna Loa volcano in Hawaii detected in the atmosphere, over the course of 24 hours, an average carbon dioxide concentration of 400 parts per million. Carbon levels have probably not been as high as that in the past 3 million years—since before human beings existed.

Human activity is responsible for the high levels of carbon dioxide, but the majority of humans burn relatively little carbon. According to the UN Development Programme, the planet's poorest 1 billion people are responsible for only 3 percent of carbon emissions. (Many of them, however, live in rural areas and urban slums that are highly vulnerable to threats associated with climate change.) Meanwhile, the 1.26 billion people who live in nations that belong to the Organisation for Economic Co-operation and Development are responsible for 42 percent of the carbon added to the atmosphere each year, and their nations are overwhelmingly responsible for the carbon that has been added in the past.

Basic values such as justice and respect for human dignity make it obvious that the people most responsible for carbon in the atmosphere—the richest one-seventh of them—should both burn less carbon and pay most to address the problems that use of fossil fuels has created. But burning fossil fuels is highly addictive. People who are hooked on it will try every trick they can think of to avoid withdrawal symptoms.

One such trick is to burn carbon derived from Earth's surface (biomass) instead of carbon deposits extracted from underground (fossil fuels). The idea appears at first to make sense, as biomass when burned emits the same amount of carbon as has been stored during the biomass's growth phase; this should result in no net increase of atmospheric carbon. But things are not so simple when the idea is applied on an industrial scale and all inputs and indirect effects are taken into account.

The European Environment Agency Scientific Committee argues that bioenergy "is meant to reduce [emissions of greenhouse gases] but … increases the amount of carbon in the air … if harvesting the biomass decreases the amount of carbon stored in plants and soils, or reduces ongoing carbon sequestration." And many have argued that biofuels in particular actually use more energy than they produce. Moreover, replacing fossil fuels with bioenergy implies that an enormous amount of agricultural or forest land will be diverted to the purpose. Massive deforestation and land clearing—which eliminate carbon sinks and add to total carbon concentrations—are already occurring in Indonesia and other countries due to the increasing cultivation of commodities like palm oil.

Various sensible approaches for mitigating climate change are available. Modern agricultural practices, which are responsible for 14 percent of global greenhouse gas emissions, could be replaced with organic agriculture, which can be carried out in a carbon-neutral manner and might even store large amounts of carbon in the soil. But this would require the world's wealthy to change their consumption habits, for instance by eating less meat. Forests can be regrown so they can function as carbon sinks—though this has a net effect only as long as forests are expanding. Europe's forests, which have been recovering since the 1950s after centuries of deforestation, have functioned as carbon sinks over recent decades but are showing early signs of saturation.

What's really necessary, however, is for people—especially in the wealthy world—to reduce their carbon emissions. To achieve this, it is probably necessary to introduce carbon taxes in wealthy countries. But the developed world's big emitters continue to seek other solutions. It is as if a cigarette smoker, rather than giving up tobacco, decided to move to the suburbs to breathe cleaner air. This is a fake form of compensation, and bioenergy is similar. It creates the illusion of a greener economy. It allows people to postpone tough decisions. But whereas smokers who don't give up cigarettes mainly harm themselves, wealthy countries that consume massive amounts of fossil fuels pass the harm to innocent people.

If nothing changes, it may be just as well to abandon any pretense of respect for values such as justice and human dignity. Those values have suffered for a long time in any case, as nations have failed to live up to the "common but differentiated responsibilities" that are discussed in the UN Framework Convention on Climate Change.

In his Round One essay, José R. Moreira focused on biofuels' potential to meet the need for transportation fuel while also mitigating climate change. He provided a largely positive view of biofuels, not surprising in light of the prominence that biofuels have assumed in his nation of Brazil. Roberto Bissio discussed the potential adverse impacts of bioenergy projects on forests and agricultural lands, while also devoting attention to developed countries' responsibility to reduce their carbon dioxide emissions. My colleagues maintain starkly different views, but they have one thing in common so far: large-scale bioenergy projects. I would argue that small-scale projects—because of their potential to mitigate climate change and support sustainable rural development, without undermining food security or incurring unmanageable expense—deserve a great deal of attention.

The International Energy Agency estimates that 2.7 billion people worldwide lack access to clean cooking facilities and that 1.3 billion people lack access to electricity. Most people who suffer from energy poverty—84 percent—live in rural areas. Bioenergy, the agency argues, can play a significant role in achieving global access to clean energy, notably among the rural poor. An array of modern, small-scale technologies can contribute to this effort. These include efficient cookstoves, biogas for cooking and village electrification, biomass gasifiers, and decentralized cogeneration systems that utilize bagasse (the fiber that remains after liquid is extracted from sugarcane). These biomass-based options, partly by reducing the carbon dioxide emissions that result from unsustainable biomass harvesting, could achieve a 1-gigaton reduction in annual greenhouse gas emissions. They could also reduce, by 60 to 90 percent, emissions of black carbon—essentially, soot—which is blamed for 2 million deaths each year.

A detailed World Bank study of Mexico covering the period 2009 to 2030 determined that adoption of advanced biomass stoves could, while producing a net economic benefit, reduce carbon dioxide emissions by 19.4 megatons a year—a larger reduction than could be achieved by any other action in the residential sector. A study in India, meanwhile, compared the mitigation potential of decentralized bioenergy for village electrification with the mitigation potential of carbon sequestration through forestry. The study concluded that, over 100 years, substituting biomass energy for diesel fuel would prevent 92.5 tons of carbon per hectare from entering the atmosphere. The forestry projects would achieve less. Long-rotation projects would keep 45.2 metric tons of carbon per hectare out of the atmosphere, while short-rotation projects would keep only 23.9 tons per hectare out of the atmosphere.

Decentralized applications of small-scale, modern bioenergy options—particularly in rural parts of developing countries—generally represent win-win approaches. They can provide benefits along the climatic, environmental, and social dimensions while avoiding adverse effects on food security. In discussions of biomass energy, it is important to avoid excessive focus on the large-scale production of biofuels for transportation. Other approaches exist—approaches that can mitigate climate change while presenting only minimal implications for the environment and food production.