Review of CO2 recovery methods from the exhaust gas of biomass heating systems for safe enrichment in greenhouses

Novel approaches to practice CO2 enrichment in greenhouses from the exhaust gas of a biomass heating system are reviewed. General CO2 enrichment benefits for greenhouse plant production are described along with optimal management strategies to reduce fuel consumption while improving benefits. Alternative and renewable fuels for CO2 enrichment, landfill biogas and biomass, are compared with traditional methods and fuels. Exhaust gas composition is outlined to address the challenges of CO2 enrichment from biomass combustion and leads to a comparison between combustion and gasification to improve boiler efficiency. In terms of internal modifications to a biomass heating system, syngas combustion, following biomass gasification, presents good potential to achieve CO2 enrichment. Regarding external modifications to clean the exhaust gas, CO2 can be extracted from flue gases via membrane separation that has shown a lot of potential for large industries trying to reduce and isolate CO2 emissions for sequestration. Other research has optimized wet scrubbing systems by extracting SO2 and NO emissions from flue gases to form ammonium sulphate as a by-product valuable to fertilizer markets. The potential of these techniques are reviewed while future research directions are suggested.