Decarbonising Agricultural Heat

Heating can account for around 30% of energy use on farms and is used in greenhouses and polytunnels, drying arable crops, livestock production and heating farm buildings. Agriculture contributes 11% of the UK's carbon dioxide emissions and heating systems have their part to play in this, as the vast majority are run by burning fossil fuels such as natural gas and diesel.

Government has committed the UK to achieving net zero carbon by 2050 and has identified the agricultural sector as one in which taking measures to decarbonise heat will not be cost effective - (2021 Net Zero Strategy).

The answer does not seem straight forward but here at Freeths LLP, we are seeing increased investment in a range of methods for generating low carbon heat, which often present multiple revenue making opportunities. This has been brought into sharp focus with the recent hikes in gas and electricity prices, incentivising farmers to generate their own gas and electricity, and sell the excess to the market at very attractive rates as a low-carbon source.

Anaerobic digestion

This a natural process which uses micro-organisms to break down plant and animal materials in the absence of oxygen in order to produce a methane-rich biogas. Large digesters can be fed on food and farm waste, slurry, manure and crops such as maize, and so are ideal farms looking to diversify.The biogas produced by the digesters can be used to generate low carbon heat. Networks of pipes and heat exchangers can deliver heat across the farm for its relevant uses and can provide heat to neighbouring properties via heat network connections. This dramatically reduces the amount of natural gas that the farm has to purchase from the gas grid.If the capital cost of constructing an anaerobic digester is a disincentive, there are plenty of corporate and venture capital investors willing to fund or develop projects which provide long-term revenue. The farm owner benefits from rental income for the land upon which the digester sits, and low-cost heat/electricity to use on site.

This is especially the case where electricity is generated alongside the heat with the addition of a combined heat and power system.  Energy companies are falling over themselves to find sources of electricity which can be badged as low carbon. At Freeths, we have seen a sharp up-tick in such Power Purchase Agreements (PPAs) for the sale of electricity. Excess biogas produced by the digester can also be sold to third parties via export to the gas grid, which the Government is financially incentivising through the Green Gas Support Scheme, launched in November 2021.

One by-product of anaerobic digestion is digestate, which can be used and sold as fertiliser. Another by-product is carbon dioxide which, if captured rather than being released into the atmosphere, can enable the system to be carbon negative. Liquification plants capture the carbon dioxide, which can then be sold for use in fizzy drinks, food products, refrigerators etc.

Chicken litter biomass

A quirky opportunity which only became legal in 2015 is the burning of chicken litter in biomass boilers, to generate heat in the form of hot water. This hot water can then be pumped around the farm as a heating system for various uses - although it seems only fair that the poultry sheds get priority!This innovative concept is a sustainable and low-carbon source of heat, and puts this waste product to good use. Used at scale, there is no reason why a combined heat and power system could also be used to generate low-carbon electricity.

Geothermal energy

Geothermal energy harnesses heat from within the rock and fluid contained underground. Heat in the form of hot water and steam is extracted by large bore holes or “wells” and can be put to a variety of uses. It is a stable and reliable heat source, reducing reliance on the consumption of costly natural gas.It has become popular in the agricultural sector on the continent, particularly the agri-food industry in the Netherlands and France. It has obvious uses in greenhouses, polytunnels, soil heating and aquaculture but, at scale, the hot water can be used to heat local neighbouring communities, via heat networks. The UK is yet to embrace geothermal energy as a solution to the conundrum of decarbonising heat but if the Government is serious about tackling climate change, it could be a serious contender to include in the mix. 

Inspired?

If any of the above has given you food for thought, don't hesitate to contact our heat network team to find out more.