LOW CARBON AND RENEWABLE ENERGY OPTIONS FOR FARMS
Royal Agricultural Society of England
Solar PV farm installations continue to grow. Small on-shore wind has regained popularity due to its ability to extend generation throughout the year with addition of battery storage for use on-site and at peak times in an increasingly flexible grid.
Although UK agriculture does not produce many of the country’s direct CO2 emissions from energy use, exposure to volatile or increasing energy prices will adversely affect the profitability of farm businesses and their costs of production. Pricing issues are likely to become more common as countries decarbonise or where climate-related events such as flooding or prolonged cold affect fossil fuel supply chains.
On-farm energy generation should therefore be promoted as a way of increasing resilience and as an untapped rural investment opportunity - an essential part of the process of decarbonizing agriculture. With the trend towards electrification where possible, distributed, ‘behind-the-meter’ (i.e. on-site) energy production can present some attractive new opportunities for farm businesses. On-site electricity generation also helps to minimise the demand on weak rural electricity grids. UK farms must continue to invest in appropriate renewable energy technologies for heat, electricity and fuel: e.g. solar photovoltaics, wind turbines, heat pumps, solar thermal, biomass, anaerobic digestion (AD) of farm residues, plus battery storage and micro-/pico-hydroelectric. Integration of multiple technologies is important as it can increase the times that intermittent renewables can be used, e.g. photovoltaics/wind/battery for electricity or solar thermal/heat pump/solar PV for heat.
Although technology is still developing, the UK is in a favourable position with its increasingly ‘smart’ and ‘flexible’ electricity grid, which uses technologies such as artificial intelligence (AI) and smart devices to match demand with supply increasingly sourced from distributed electricity generation from intermittent renewables (e.g. wind and solar) and storage (e.g. batteries; pumped water storage). Such innovation enables farm businesses to adjust their electricity requirements to take advantage of on-farm generated and stored power or cheaper off-peak tariffs at times of cheapest electricity.
Anaerobic Digestion (Biogas and Biomethane)
Despite over 15 years of efforts to promote biogas with generation incentives, farm scale anaerobic digestion, based on livestock, local and crop residues, has largely failed to deliver multiple on-farm AD plants, tailored to the needs of local communities.
With the UK’s Net Zero commitment and increasingly volatile energy prices, it is time for the reassessment of the role of smaller-scale on-farm biogas sites, which can be carbon-negative, particularly when manures/slurries and local rural food wastes are used as feedstock. Because AD is part of the carbon cycle, returning recalcitrant carbon back to land and intercepting volatile carbon in the form of energy, it is a perfect way to capture and utilise carbon emissions which would have been emitted anyway via uncontrolled biodegradation.
The role of biogas in the transition to greater resource efficiency in the agri-food sector has been understated. GHG mitigation is only one benefit of on-farm biogas. Apart from energy supply, other significant benefits include fossil fertiliser replacement, weed seed reduction and improved animal health, with treated digestate spread on grazing land and not raw slurry. Rural areas can benefit from reduced food waste miles if local organic wastes are used to supplement slurry/manure feedstocks.
At this smaller, more ‘human’ scale, it is also easier to work with the community to minimise food waste contamination (e.g. plastics), producing a cleaner digestate, supporting the ‘proximity principle’ with a circular economy practice and recycling the nutrients back to land.
The biogas is used to produce 24/7 electricity and heat through a combined heat and power (CHP) unit, or heat only through a boiler - or it can be upgraded to biomethane. Off-grid upgrading for use as a vehicle fuel or to replace natural gas in applications such as heating is feasible and less complex than grid injection. Some plant designs include piping biogas/biomethane to a central injection point.
The agricultural sector offers a unique opportunity for biomethane within a more circular economy, as an adoption-ready option to deliver early diesel replacement for tractors and HGVs. Incentivising adoption-ready technologies is important in reducing emissions now, whilst other technologies catch
up. Also, on-site biomethane offers a route to the phasing out of the red diesel subsidy prior to 2030.
Unlike many off-site carbon capture and storage projects using dilute CO2 streams, on-farm biomethane upgrading offers a perfect opportunity to further improve the GHG credentials of its production since it is straightforward to capture the CO2 produced in the process. This CO2 can be cleaned up to food grade standard or it can be compressed and injected underground to sequester it.
To read the full report by the Royal Agricultural Society of England click in the link to download the document or go directly to their website here.