Using BEAM*2022 to Quantify the GHG Benefits of Beneficial Use of Biosolids and Biogas
The Biosolids Emissions Assessment Model (BEAM*2022) is an Excel spreadsheet-based GHG accounting model focused on solids management that can be used to develop baseline GHG emissions inventories and evaluate up to 10 solids processing and end-use alternatives. Originally developed in 2009 by the Canadian Council of Ministers of the Environment, the BEAM model was updated in 2022 by the North East Biosolids & Residuals Association (NEBRA) and Northwest Biosolids and published as BEAM*2022.
BEAM*2022 uses up-to-date and scientifically-backed emission factors and allows for consistency in calculating GHG emissions across wastewater agencies. The model is transparent by listing all process assumptions, emission factors and their corresponding sources. The model will be regularly updated to capture scientific advances in GHG emission factors and methodologies. For that purpose, a science review team of five PhDs has been formed to conduct annual reviews and implement updates to the model.
BEAM*2022 and its supporting documents are available for download with a recommended sliding-scale donation at BiosolidsGHGs.org. The website also hosts a place where wastewater agencies that have used BEAM*2022 can share their GHG emissions data, findings, and lessons learned.
To read more about BEAM*2022, see Measuring Biosolids Impacts on Climate Change and Resiliency (NEWEA Journal, Volume 56, No.1, Spring 2022).
SFPUC’s Case Study
Recently, SFPUC utilized BEAM*2022 to calculate its net GHG emissions from various biosolids management processes and biogas utilization alternatives to better understand their carbon impact. SFPUC’s analysis showed that beneficial use of biosolids and biogas resulted in a net reduction of GHGs in the atmosphere.
By land applying and composting biosolids from both the Southeast Treatment Plant (SEP) and Oceanside Water Pollution Control Plant (OSP), SFPUC avoided putting nearly 4,000 metric tons of carbon dioxide equivalent (CO2eq) emissions in the atmosphere in 2022.
Anaerobic digestion is used to make biosolids and it also produces methane gas, otherwise referred to as biogas. This gas can be cleaned and used to generate electricity and heat (cogeneration), it can be used to fuel vehicles or put into the natural gas grid. If the gas is not utilized, it must be flared (converted from methane to carbon dioxide). Because SFPUC’s cogeneration systems at SEP and OSP were offline in 2022, the biogas produced during anaerobic digestion was flared and there was a net generation of 1,486 metric tons of CO2eq emissions. The good news is that the SEP cogeneration system is back in service and, at the time of this post, is converting biogas into 1.5 megawatts of renewable energy. The OSP cogeneration system is currently under construction and should be online in 2025.
Using BEAM*2022, the SFPUC was also able to quantify how better utilization of biogas results in a net reduction of GHG emissions. Currently, SEP is able to utilize 70% of its biogas for boiler and cogeneration use, meaning 4,957 metric tons of CO2eq emissions can be avoided annually. This is equivalent to removing 1,102 gasoline-powered passenger vehicles from the road for one year. In the future, SEP plans to inject 100% of its biogas as renewable natural gas into the gas grid. This will represent 6,113 metric tons of CO2eq emissions avoided annually. This is equivalent to removing 1,360 gasoline-powered passenger vehicles from the road for one year.
