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What does the future hold for digestate use on farms?

BioVale Anaerobic Digestion Special Interest Group (ADSIG)

Our latest AD SIG event used expert talks from the NFU, ADBA and Aqua Enviro to frame facilitated discussions around how regulatory changes might impact on the use of digestate as a bio-fertiliser.

A number of rules and guidelines are in place to avoid potential pollution of land air and water from digestate via plastics, ammonia or nitrates, including: Farming Rules for Water and RPS 252, AD Quality Protocol and Environmental Permitting. The Environment Agency is currently reviewing its approach to the use of sewage sludges on farmland, most of which are AD digestates – and the overall picture is that digestate regulation is getting tighter, with future measures already including:

  • requirements to use low-emission spreading equipment
  • a need for rapid incorporation
  • covering and gas capture at slurry and digestate stores
  • more farm inspections

Other countries are further down this road. In the Netherlands, Denmark and Flanders, high livestock densities have led to measures such as: manure and digestate dewatering to facilitate export of P in the fibre (and allow biological treatment of the liquor to remove nitrogen), farm-specific N quotas, centralised nutrient record-keeping, catch crop requirements and agronomic N & P ceilings.

AD digestate used as a fertiliser on farmland can help decarbonise agriculture and moves us toward a more circular economy: things that policy makers want. So are there any incentives? There is grant funding to buy equipment, including storage facilities: from the Farming Equipment and Technology Fund and the forthcoming Slurry Investment Scheme. However, despite many references to low-carbon agriculture, it looks like the Environmental Land Management Scheme (ELMS) will do little to directly encourage digestate use.

So, how well is the industry coping with the changing regulatory landscape and how do they feel about the future? To discuss the issue, we brought together a total of  35 participants in four discussion groups, each containing farmers, AD operators, experts and researchers. Some common themes emerged across the groups:

With rising prices for artificial fertilisers and only 8% of UK farms taking organic fertilisers, there is strong demand for digestate as a fertiliser.

Small on-farm AD plants are great models of the circular economy, but they are finding it hard to comply with an increasing regulatory burden. Without support to help them navigate this regulation successfully, small-scale AD businesses are likely to go out of business.

Constraints around autumn spreading of digestate are seen as inflexible and enforcement doesn’t necessarily reflect local conditions, where they may be nutrient demands for winter cereals and cover crops.

Storage is a real issue. It is important for nutrient management but expensive to install and new requirements are likely to make it more expensive still.

Efforts to control plastic pollution on farmland are likely to become more stringent in England and align with current regulations in Scotland – but where does the responsibility for improvement lie – with the waste management company, the digestate provider or the farmer?

There is potential for digestate to find new uses – for example, as a fertiliser for use in horticultural or domestic context or for algal production. The regulators want more data before considering widening its use but firms are unwilling to try new things unless regulatory barriers to market are low- how do we get out of this Catch22 situation?

Multiple sets of regulations and guidelines govern this area and they can be hard to navigate or may even seem to be contradictory. What’s more, regulatory changes are creating uncertainty that acts as a barrier to investment.

As usual, the SIG has a special interest in how research and innovation may provide solutions for the AD industry.  Several participating companies have new solutions to reduce ammonia emissions from AD.

  • Azotics uses nitrogen-fixing bacteria to provide a sustainable solution to fertiliser overuse.
  • Bioelements have microbial products, for use in lagoons and slurry pits.
  • N2 applied have developed a plasma technology to reduce ammonia emissions from digestate during storage and after field application.

There seems enough going on here to merit a future ADSIG event focusing on innovation to address pollution from AD. If you have suggestions for a topic you would like covered by us in the future, contact elspeth.bartlet@york.ac.uk.

Elspeth Bartlet

Elspeth Bartlet, BioVale