Policymakers look at biomass as attractive for generating electricity because it produces lower greenhouse gas emissions than coal does. But a new study suggests this isn’t the best use of biomass, an energy source made from plant matter. Researchers report that burning biomass instead of fuel oil to heat homes is a far cheaper way to cut greenhouse gas emissions (Environ. Sci. Technol., DOI: 10.1021/es202752b).
Boilers that burn fuel oil are popular in the northeastern U.S. to heat homes and businesses, says Tom Wilson, a manager of energy efficiency programs at Pacific Gas & Electric Company, and lead author of the study. Recently, boilers that run on biomass such as compressed switchgrass pellets have become an alternative. When Wilson noticed that, per unit of energy content, the price of biomass was less than one-fifth the price of fuel oil, he wondered whether using biomass to heat homes was a cost-effective way to cut carbon dioxide emissions–and whether it would be a better performer there than in power plants.
So Wilson, then a graduate student at Pennsylvania State University, his advisor Paul Adler, and their colleagues estimated the cost to cut 1 ton of CO2 emissions by swapping biomass for coal in a power plant and by replacing fuel oil with biomass in a commercial or home boiler. For each scenario, they first conducted a life cycle assessment to estimate greenhouse gas emissions from biomass use. They did so by adding up CO2 produced at each step, including growing the plants, compressing biomass into pellets, and transporting and burning the pellets. The researchers compared those emissions to estimates from earlier studies on emissions from coal-powered electricity and fuel oil heating.
Next Wilson’s team calculated the costs of using biomass. They considered the costs of growing the plants, as well as buying and operating equipment to burn the biomass. As a comparison, the researchers used U.S. government data for the costs of burning fuel oil and coal.
Based on their emissions and cost calculations, the researchers found that saving a ton of CO2 costs $149 when a power plant substitutes biomass for coal. But replacing fuel oil boilers with ones that burn biomass actually saves $52 for every ton of CO2 abated, Wilson says. He estimates that if the northeastern U.S. replaced all of its yearly 20.9 billion L of fuel oil with biomass pellets, the region could cut CO2 emissions by 45 million tons and save $3.9 billion.
Andrew Huemmler of the University of Pennsylvania, says governments in northeastern state are currently offering financial incentives for consumers to replace old fuel oil boilers. He thinks the study shows that there could be a viable market for new boilers that utilize switchgrass.