Bioenergy production would boom and spur steep reductions in greenhouse gas emissions if a global price is slapped on carbon, Massachusetts Institute of Technology researchers say in a report released today.
Examining bioenergy production under a $15-per-metric-ton carbon price that would rise steadily to $59 in 2050, researchers found production hitting 150 exajoules by 2050 -- compared with below 50 exajoules without a carbon price.
Global greenhouse gas emissions would plunge 16 percent under that scenario, the report says, cautioning that the carbon price studied doesn't take into account land-use changes. Taking into account emissions from land-use changes, including deforestation, it says greenhouse gas reduction would be nearly 60 percent from the no-carbon-price baseline.
"The study is one of the most in-depth evaluations to date of how bioenergy might fit into a low-carbon future," MIT said in a release. "The research team developed a cutting-edge modeling tool covering a comprehensive range of bioenergy pathways."
The MIT Joint Program on the Science and Policy of Global Change says its study goal was to see how bioenergy would compete with other low-greenhouse-gas options on a level playing field.
The researchers used the Economic Projection and Policy Analysis model to create both the carbon price scenarios and assumptions about economic, productivity and population growth without a carbon price. The model examined seven first-generation biofuel crops and two cellulosic biofuel conversion technologies -- bioelectricity and heat.
The model also accounted for international trade, ethanol blending limits, changes in land and production costs, and existing policies such as the federal renewable fuel standard, among other factors.
"Biofuels are only one channel for bioenergy," said Niven Winchester, an environmental energy economist at MIT. "If you want to study how land can be used to meet our energy needs, you have to think of all the different ways to use what grows on that land -- including food, feed and fuel."
The carbon price scenario resulted in efficiency improvements and energy use reductions, the report says. Electricity consumption in 2050 dropped 19 percent, while there was 73 percent less electricity from coal.
With a carbon price in the MIT model, bioenergy use rose from 8.5 exajoules in 2015 to 152.4 exajoules in 2050 -- or about a quarter of global energy needs.
The model found that corn ethanol would be produced in the United States until 2025, when it would become uneconomical.
After 2025, cellulosic ethanol would become the primary form of bioenergy; by 2020, cellulosic ethanol would account for about 57 percent of the globe's total bioenergy consumption.
Increased energy prices under a carbon price would make grasses -- one of the main inputs for cellulosic ethanol -- more attractive, while cellulosic producers would face lower land costs than other biofuel producers, according to the report. Rising electricity prices would also increase the revenue that cellulosic producers could receive from producing electricity as a co-product.
Africa and Brazil would become the largest bioenergy producers in a world where cellulosic ethanol is the main form of bioenergy, the MIT study found.
"Africa can become a key player in supplying global energy, if agricultural expertise can be transferred to this region," Winchester said. "It has the right climate and a large amount of land, but also the potential for deforestation if policy safeguards aren't in place."
The growth in cellulosic ethanol assumes that production costs fall over the next 35 years and that ethanol-blending constraints disappear by 2030 partly through the use of more flex-fuel cars.
MIT found that pricing greenhouse gas emissions from bioenergy land-use changes significantly increases the amount of greenhouse emission reductions that occur as a result of bioenergy expansion.
Pricing land use changes would prompt a global reforestation of 800 million hectares between 2010 and 2050, according to the study. In 2050, cumulative carbon-dioxide-equivalent emissions would be 37,381 million metric tons if land-use changes were priced, compared to 74,140 million metric tons if they were not.
"The report concludes that changes spurred by the carbon price, including bioenergy production, could cut greenhouse gas emissions by more than half, with a catch -- to achieve the cut, the carbon price must cover emissions from changing land use," MIT said. "Without this safeguard, deforestation becomes a major concern as forests are cleared to make way for farmland."
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