In this study, we estimate potential synergy between pollution and climate control in the U.S. and China and conduct a cross-country comparison. When measured as cross-emissions elasticity, ancillary CO2 abatement from unit % reduction of NOx and SO2 emissions is substantially greater in China under stringent targets, though comparable between the two countries under moderate targets. In contrast, NOx and SO2 abatement from unit % reduction of CO2 emissions is much greater in the U.S. than in China, regardless of the stringency of the policy shock. These results are primarily driven by China’s higher dependence on coal, as coal has larger unit emission-reduction effects than other fossil fuels and its intensive use creates more room for less costly fuel-switching and abatement options. In addition, pollution-abatement co-benefits of carbon mitigation tend to be greater than carbon-mitigation co-benefits of NOx and SO2 reduction in the U.S., while the opposite is the case for China. The relatively low pollution-abatement effects of carbon mitigation policy in China are primarily due to the expanded role of carbon capture and storage technology, which keeps coal from being crowded out of the energy market by reducing its carbon emission factors, but without affecting NOx and SO2 emissions. Our study suggests that some countries like China may consider it more appealing to pursue the synergy from a pollution-control perspective than from a carbon-mitigation standpoint, given the former’s greater synergistic effects. In this sense, future co-benefit studies need to pay more attention to carbon co-benefits of pollution abatement—the opposite logic of the currently dominant focus.

What will large-scale global bioenergy production look like? We investigate this question by developing a detailed representation of bioenergy in a global economy-wide model. We develop a scenario with a global carbon dioxide price, applied to all anthropogenic emissions except those from land-use change, that rises from $15 per metric ton in 2015 to $59 in 2050. This creates market conditions favorable to biomass energy, resulting in global non-traditional bioenergy production of ~150 exajoules (EJ) in 2050. By comparison, in 2010 global energy production was primarily from coal (139 EJ), oil (175 EJ) and gas (108 EJ). With this policy, 2050 emissions are 16% less in our Base Policy case than our Reference case, although extending the scope of the carbon price to include emissions from land-use change would reduce 2050 emissions by 57% relative to the same baseline. Our results from various policy scenarios show that lignocellulosic (LC) ethanol may become the major form of bioenergy, if its production costs fall by amounts predicted in a recent survey and ethanol blending constraints disappear by 2030; however, if its costs remain higher than expected or the ethanol blend wall continues to bind, bioelectricity and bioheat may prevail. Higher LC ethanol costs may also result in expanded production of first-generation biofuels (ethanol from sugarcane and corn) so that they remain in the fuel mix through 2050. Deforestation occurs if emissions from landuse change are not priced, although the availability of biomass residues and improvements in crop yields and conversion efficiencies mitigate pressure on land markets. As regions are linked via international agricultural markets, irrespective of the location of bioenergy production, natural forest decreases are largest in regions with the lowest political constraints to deforestation. The combination of carbon price and bioenergy production increases food prices by 2.6%–4.7%, with bioenergy accounting for 1.3%–2.6%.

Be Cautious about Bioenergy, but Don't Rule It Out

Research commentary by Niven Winchester in response to the World Resources Institute report on biofuels and bioenergy.

A report published by the World Resources Institute (WRI) in January has reignited the old debate over biofuels and other forms of bioenergy, casting doubt on their climate benefits and effects on food availability. With recent low oil prices, and the EPA set to announce updated biofuel standards in the spring, the stakes for considering what role bioenergy will play in a sustainable future are higher than ever.

While the WRI report’s authors outline valid reasons to be cautious about bioenergy, the report contains misleading statements about the role of bioenergy in abating emissions.

The report claims that bioenergy made from fuel crops does not reduce direct carbon emissions because, say, diverting maize from food to ethanol does not result in additional absorption of carbon. While this is true, focusing on direct emissions is short-sighted because it doesn’t take into account the bigger picture of where energy comes from. Regardless of whether maize is used for food or fuel, emissions absorbed will end back into the atmosphere, mainly through respiration in the former and combustion in the latter. However, if maize is used for ethanol, it displaces oil and reduces carbon emissions.

If direct emissions were used to evaluate solar power, this technology would also be judged not to reduce carbon emissions, as no emissions are either stored or released when sunlight is converted to electricity. This is not to say that the carbon benefits from bioenergy are equal to the emissions from the fossil energy that it displaces. Growing bioenergy crops requires energy to plant, harvest and process, and may result in deforestation. Emissions from these activities reduce the carbon benefits of bioenergy, but there is still the potential for it to reduce emissions.

The report also claims that bioenergy analyses double-count land by assuming that biomass for other purposes, like food and lumber, continue to be met when land is used for bioenergy. In fact, studies that consider the economy-wide effects of bioenergy cultivation explicitly represent resource constraints, so land used for bioenergy cannot be used for other purposes. In these studies, as in the real world, increased demand for land to grow bioenergy crops will increase land prices.

The effects of the higher land prices propagate throughout the economy in several ways. Land may be used more intensively by, for example, developing new cultivars. On the other side of the equation, demand for food can be reduced through greater use of refrigeration and packaging to reduce food waste.

That is, incentives for bioenergy can drive efficiency improvements in crop production and use that allow food and fuel demands to be met using limited resources. These efficiency improvements come at a cost, but so do other carbon abatement options.

Bioenergy is not a “silver bullet” against climate change, has been over-hyped in some circles, and governments should guard against negative impacts on water and biodiversity. At the same time, bioenergy should not be erroneously excluded from our toolkit for fighting climate change, because we will need all the tools available to us.

Niven Winchester is an environmental energy economist at the Joint Program on the Science and Policy of Global Change. He is a coauthor of the recent report "The Contributions of Biomass to Emissions Mitigation under a Global Climate Policy."

We assess the ability of global water systems, resolved at 282 assessment subregions (ASRs), to the meet water requirements under integrated projections of socioeconomic growth and climate change. We employ a water resource system (WRS) component embedded within the Massachusetts Institute of Technology Integrated Global System Model (IGSM) framework in a suite of simulations that consider a range of climate policies and regional hydroclimate changes out to 2050. For many developing nations, water demand increases due to population growth and economic activity have a much stronger effect on water stress than climate change. By 2050, economic growth and population change alone can lead to an additional 1.8 billion people living under at least moderate water stress, with 80% of these located in developing countries. Uncertain regional climate change can play a secondary role to either exacerbate or dampen the increase in water stress. The strongest climate impacts on water stress are observed in Africa, but strong impacts also occur over Europe, Southeast Asia, and North America. The combined effects of socioeconomic growth and uncertain climate change lead to a 1.0–1.3 billion increase of the world’s 2050 projected population living with overly exploited water conditions—where total potential water requirements will consistently exceed surface water supply. This would imply that adaptive measures would be taken to meet these surface water shortfalls and include: water-use efficiency, reduced and/or redirected consumption, recurrent periods of water emergencies or curtailments, groundwater depletion, additional interbasin transfers, and overdraw from flow intended to maintain environmental requirements.

© 2014 the authors

We use an economy-wide model to estimate the impact of a representative climate policy on fuel prices and economic activity, and a partial equilibrium model of the aviation industry to estimate changes in aviation carbon dioxide emissions and operations. Between 2012 and 2050, with reference demand growth benchmarked to ICAO/GIACC (2009) forecasts, we find that aviation emissions increase by 130 per cent. In our policy scenarios, emissions increase by between 103 per cent and 123 per cent. Under the assumptions in our analysis, aviation contributes to climate policy targets by funding emissions reductions in sectors with less costly abatement options.

© 2013 Journal of Transport Economics and Policy