A resurgence in the use of biomass to produce energy is underway, in part as a way for countries to continue the transition away from fossil fuels for electricity production. Groups are working on ways to burn what otherwise might be waste products to provide power, particularly in areas where access to electricity has been lacking.
1. Rice straw, the vegetative part of the rice plant, can be burned, making it a viable source of fuel for biomass-fueled power plants in some areas of the world. Scientists are developing ways to use unwanted rice straw to produce energy at a commercial scale. Source: Creative Commons / Toshihiro Matsui
Researchers at Aston University in Birmingham, England, are involved in a project to use biomass from Indonesia’s unwanted rice straw (Figure 1) to produce low-cost energy at a commercial scale. PT Perusahaan Listrik Negara (PLN), Indonesia’s government-owned power corporation, is implementing biomass co-firing technology at its power plants to replace retiring coal-fired power generation. The U.S. Congress recently passed two bills—the National Defense Appropriations Act of 2023 and the Omnibus Appropriations legislation—that recognize the benefits of biomass as a source of renewable electricity. Carrie Annand, executive director of the Biomass Power Association, said, “Utilizing organic materials like forest residues and agricultural waste to generate power undeniably supports our nation’s climate goals. Not only do biomass power plants generate renewable power, but they also provide forest health and air quality benefits by helping to reduce forest fire risk and preventing the need for open burning.”
The International Energy Agency (IEA) in a 2022 report outlined a 10-point plan to reduce the European Union’s reliance on Russian natural gas and said dispatchable low-emission generation from bioenergy should be maximized. The IEA reiterated its stance in a joint project with the European Climate Foundation, in which the groups said increasing biomass use in heat and power could offset the use of as much as 2 billion cubic meters of natural gas. The agency has said it expects global biofuel demand to grow by 20% over the next five years, and said “policies designed to reduce GHG [greenhouse gas] emissions are driving demand because these fuels can be produced with low GHG emissions, blended at high levels, and made from wastes and residues. In fact, nearly 70% of renewable diesel and biojet fuel came from wastes and residues in 2021.”
Researchers at the Indian Institute of Science (IISc) in India recently said it is possible to obtain hydrogen gas using biomass as an energy resource. The team was led by S Dasappa, professor at the Centre for Sustainable Technologies, and Chair of the Interdisciplinary Centre for Energy Research at IISc. India uses hydrogen for several processes in different sectors, and Dasappa said the hydrogen market is expected to grow substantially in the coming years. “But most of the hydrogen we currently use comes from fossil fuels through a process called steam methane reforming route,” Dasappa said, noting that his team has found a way to extract green hydrogen from biomass in a two-step process.
The researchers said the first step involves converting biomass into syngas, a hydrogen-rich fuel gas mixture, in a reactor using oxygen and steam. The second step involves generating pure hydrogen from syngas using a low-pressure gas separation unit. Both those technologies have been developed in Dasappa’s lab.
The researchers said the process “is a highly efficient method of generating green hydrogen—it produces 100 g [grams] of hydrogen from 1 kg [kilogram] of biomass even though only 60 g of hydrogen are present in 1 kg of biomass. This is because in this process, steam, which also contains hydrogen, participates in both homogeneous and heterogeneous reactions [in homogeneous reactions, reactants are in a single phase, whereas in heterogeneous reactions, the reactants are in two or more phases].” Dasappa said the technology aligns with India’s National Hydrogen Energy Roadmap, a government initiative to promote hydrogen as a fuel and lessen the country’s dependence on fossil fuels.
The project at Aston University would help Indonesia in several ways. The country produces about 100 million metric tons of rice waste each year; officials said about 60% of that waste is burned in open fields, contributing to air pollution. Those officials said the amount burned is equivalent to about 85 TW of electricity. The Aston project is designed to capture some of that energy to provide Indonesia with more electricity.
The process uses pyrolysis, a biomass conversion technology that involves heating organic waste materials—in this case rice waste—to about 500C. This breaks down the organic material, producing vapor and some solid products. Pyrolysis oil can be made by condensing the vapor into a liquid; both pyrolysis vapor and the bio-oil can be converted to electricity, according to the researchers.
Carnot Limited, a member of the consortium supporting the Aston research, has patented a combustion energy technology that it says could convert about 70% of the thermal energy of the straw into electricity, or double the amount currently being converted. In addition to its research, the project wants to develop a business model to generate electricity on Indonesia’s Lombok Island, with a goal to expand it to other countries with the potential to burn biomass.
Dr. Jude Onwudili, leading the research team at Aston University’s Energy and Bioproducts Research Institute, in a news release said, “This project has huge potential—commercialization of this combined technology will have significant economic benefits for the people of Indonesia through direct and indirect job creation, including the feedstock supply chain and electricity distribution and sales. About one million Indonesian homes lack access to energy and Indonesia’s 6,000 inhabited islands make sustainable infrastructure development challenging in areas such as Lombok Island. The new techniques being explored could reduce environmental pollution, contribute to net zero, and most importantly, provide access to affordable energy from sustainable local agricultural waste.”
Aston’s project team has calculated that over a power plant’s life, biomass produces cheaper electricity compared to other fuels, including solar and geothermal, along with coal and natural gas. The project is set to ramp-up in April with a total of£1.5 million ($1.8 million) in funding for the four partners from Innovate UK. The Aston team, in addition to aligning with Carnot Limited, also is working with two other UK-based businesses—PyroGenesys and Straw Innovations—on the project. PyroGenesys specializes in PyroChemy technology, which it says can convert 70% of the rice straw into vapor or bio-oil for electricity production. The rest of the rice waste will be converted into nutrient-rich biochar, which can be used as fertilizer on rice or other farms. Straw Innovations will contribute its expertise in rice straw harvesting and collection, which it has done for many years in Asia.
Officials with PLN said the state-owned power producer is implementing biomass co-firing technology at 33 coal-fired power plants, and over the next few years will add the technology to another 52 coal-fired units. Evy Haryadi, director of transmission and system planning at PLN, at the recent COP27 meeting in Egypt said the co-firing program will help reduce power plant emissions, and also provides an economic opportunity for customers who want their household waste, including organic material, to be processed and converted into biomass pellets that could be burned at the power plants.
Dasappa said the technology being developed by the team at IISc to use biomass to create hydrogen could be used to help decarbonize the steel industry. He also said it could be used for ethanol and methanol production. Researchers at NITI Aayog, an Indian government think-tank, in a recent white paper wrote that “hydrogen demand in India could grow more than fourfold by 2050, representing almost 10% of global hydrogen demand.” In addition, the paper said the use of green hydrogen could result in 3.6 gigatonnes of cumulative CO 2 emission reductions between 2020 and 2050. Government officials said the Indian Oil Corp. also will be involved in scaling the technology; the group has said it wants at least 0.25 metric tons of hydrogen per day to use in fuel cell-powered buses.
—Darrell Proctor is a senior associate editor for POWER (@POWERmagazine).