Lemont, Illinois based science and engineering research centre, Argonne National Laboratory (ANL), has developed technology that synergistically uses two waste biomass streams to generate two bioproducts and enhance the process of anaerobic digestion.
According to the organisation, the digestion of wastewater can be improved sludge by incorporating biomass-derived, carbon-sequestering char within the digester, thus creating pipeline-quality renewable natural gas while using the remaining biosolids for a high-quality fertiliser.
With funding from the U.S. Department of Energy’s (DOE’s) Bioenergy Technologies Office (BETO) totaling $1.5 million over three years, researchers at ANL said they have been able to develop and de-risk this technology, which is now ready for scale-up.
Biochar, charcoal derived from plant material, is created in processes such as gasification and pyrolysis, which also produce energy in the form of syngas or liquid fuels.
ANL said that it has demonstrated success using biochar from gasification of agricultural waste such as both corn stover and waste wood sources.
Anaerobic digestion usually creates biogas that is mainly a combination of carbon dioxide (CO2) and methane, and extra steps are required to upgrade the biogas to renewable natural gas by removing the CO2 and other contaminants.
However, according to ANL by adding biochar directly to the anaerobic digester sequesters the CO2 and creates a biogas stream that is more than 90% methane and less than 5 parts per billion hydrogen sulfide, thus reducing the need for upgrading steps.
The biochar was also said to improve many of the operating conditions for anaerobic digestion, and furthermore, it is nutrient-rich, so the digestate left after the process is completed can serve as a high-quality fertilizer.
With the success of this research, ANL said that it is preparing to scale up the technology with St. Louis, Missouri based Roeslein Alternative Energy (RAE)which owns and operates renewable energy production facilities that convert agricultural and industrial wastes, along with biomass feedstocks to renewable natural gas and sustainable co-products.
The company plans to perform field demonstrations during 2017 and drive the commercialisation of the technology. It is hoped that ANL’s technology could dramatically improve the economics of anaerobic digestion projects.
ANL said that the reduction of upgrading steps alone could make many smaller biogas projects become profitable. The technology was also claimed to further reduce capital and operating expenses by improving digester conditions and producing fertilizer, which would provide even greater economic benefit.
The project at ANL is part of BETO’s work to fund research, development, and demonstration of waste to energy technologies for sustainable, cost-competitive biofuels and bioproducts from cellulosic biomass.
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