Abstract
The increasing concentration of carbon dioxide (CO2) in the atmosphere and the stringent greenhouse gases (GHG) reduction targets, require the development of CO2 sequestration technologies applicable for the waste and wastewater sector. This study addressed the reduction of CO2 emissions and enhancement of biogas production associated with CO2 enrichment of anaerobic digesters (ADs). The benefits of CO2 enrichment were examined by injecting CO2 at 0, 0.3, 0.6 and 0.9 M fractions into batch ADs treating food waste or sewage sludge. Daily specific methane (CH4) production increased 11-16% for food waste and 96-138% for sewage sludge over the first 24h. Potential CO2 reductions of 8-34% for sewage sludge and 3-11% for food waste were estimated. The capacity of ADs to utilise additional CO2 was demonstrated, which could provide a potential solution for onsite sequestration of CO2 streams while enhancing renewable energy production.
Highlights
Carbon dioxide (CO2) emissions to the atmosphere need to be reduced if targets for CO2 reduction are to be met (e.g. UK Climate Change Act, 2008)
This study addressed the reduction of CO2 emissions and enhancement of biogas production associated with CO2 enrichment of anaerobic digesters (ADs)
The UK water industry emitted over 5 million tonnes of greenhouse gases (GHG) as CO2 equivalents (CO2e) during 2010–2011 (Water UK, 2012), of which 56% can be attributed to wastewater treatment (DEFRA, 2008)
Summary
Carbon dioxide (CO2) emissions to the atmosphere need to be reduced if targets for CO2 reduction are to be met (e.g. UK Climate Change Act, 2008). Conventional carbon capture and storage (CCS) is based on the long term storage of this compound in geological or ocean reservoirs (Xu et al, 2010). This still has high associated costs and significant limitations linked to the potential risk of leaking from storage sites (Holloway, 2007). The need to transport the CO2 makes the proximity of source and reservoir a limiting factor. The implementation of CCS is more feasible in large centralised sources which benefit from the pipeline’s economy of scale (Middleton and Eccles, 2013).
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