The population of the world is increasing, and with more people living in cities — a projected 70 percent of the world’s population by 2050 — people will need more energy and produce more waste. Scientists worldwide are working on projects to transform municipal solid wastes — plastics, paper and organic matter — into energy using biorefineries in urban areas.
These challenges could be addressed by biorefineries with attached paper and plastics recycling facilities. A biorefinery is similar to an oil refinery in that one plant can make many products, adjusting its output based on demand. Although in some areas, biorefinery research has focused on making a single type of bio-based fuel — such as ethanol — from a single fuel source, these new plants are working on developing energy and fuels from solid waste streams.
Integrated Waste Biorefinery
Researchers from the Indian Institute of Chemical Technology, Hyderabad, are developing an integrated waste biorefinery designed to transform wastewater and solid waste into several types of sustainable fuels, including the production of biohydrogen from wastewater. The researchers aim to produce methane, volatile fatty acids, bioplastics, biodiesel, ethanol, and other value-added chemicals.
The nation of India has great waste-to-energy potential, but is currently exploiting only about 2 percent of that potential. The nation generates 150 million tons of municipal solid waste annually, as well as 30 billion liters of sewage. A single biorefinery using 500 kilograms a day of food waste as feedstock could generate 1.32 million Indian rupees (about US$20,000) in revenue.
Researchers say integrated waste biorefineries could become feasible within five to 10 years; however, integration is the greatest challenge
Multiple Inputs and Outputs
There are many potential benefits of such a biorefinery operation, according to the National Renewable Energy Laboratory, which is researching the concept as well. It said:
By producing multiple products, a biorefinery can take advantage of the differences in biomass components and intermediates and maximize the value derived from the biomass feedstock. A biorefinery might, for example, produce one or several low-volume, but high-value, chemical products and a low-value, but high-volume liquid transportation fuel, while generating electricity and process heat for its own use and perhaps enough for sale of electricity.
These useful industrial chemicals could include lactic acid and ethanol. Biorefineries that process bagasse (fibrous sugarcane waste) are now capable of expanding into production of bio-based aviation fuel and automotive lubricant base oils, according to Technology Review, reporting on biofuels research from Lawrence Berkeley National Laboratory and the University of California, Berkeley.
In addition to meeting a country’s national energy needs, the power produced in such biorefineries could potentially contribute to consumer energy cost reductions. Greenhouse-gas emissions could be reduced.
Challenges of Scaling Up
But such changes may be slow to transpire and may require the development of more advanced, more efficient biofuel technologies. Jonathan Male, head of the United States Department of Energy’s Bioenergy Technologies Office, said:
It’s really about having the patience and persistence to stand up a new industry. […] When you start scaling up, the levels of complexity increase dramatically, as do the risks.
This has been the challenge in the United States, where many planned biorefinery projects have depended on a single feed source. The U.S. Department of Energy had planned to spend as much as $385 million within a four-year span specifically to make cellulosic ethanol; however, the fuel was deemed not as cost-effective as other options. Many projects stalled or were not completed.
Research continues supporting biorefineries able to process a range of waste products in conjunction with other types of recycling. United Kingdom scientists published their findings related to modeling the potential for this type of facility in Thailand — “Urban Biorefinery for Waste Processing” — in the journal Chemical Engineering Research and Design.
Image courtesy National Renewable Energy Laboratory.