High energy prices have led to warnings of a global fertiliser shortages, causing widespread concerns over farming crises and potential food shortages. By transitioning to anaerobic digestion (AD) and biogas, both energy and food security need could be addressed, according to the World Biogas Association (WBA).

The recovery of ammonia released during AD could help mitigate the ongoing fertiliser crisis. With ammonia a key component of fertiliser, capturing could help realise a circular economy within the industry. 

“For every kg of nitrogen lost to the atmosphere is the loss of a resource which traditionally is something like €1 or £1 per kg of nitrogen,” said Professor Mark Sutton, UK Centre for Ecology & Hydrology. 

“Currently with the fertiliser crisis we’re talking something like €3 per kg of nitrogen, this is really valuable stuff to recover.” 

By working with the UN Environment Programme, Sutton and his colleagues are working towards halving nitrogen waste, which would save about 100m tonnes of nitrogen per year. 

“This is an issue about developing a new language and new thinking. Biogas is not just about the carbon and methane, it’s about nitrogen too. I hope we can see that as part of a package that’s going to make it more economical for industry and good for the environment at the same time.” 

Bioenergy and food security 

Working to integrate bioenergy and the agriculture sector, Irini Maltsoglou, Natural Rresource Office, Deputy Energy Team Leader, FAO of the UN’s Bioenergy and Food Security (BEFS) Approach, is trying to understand the viable options from a range of perspectives including environmental sustainability, social acceptability and economic viability of the bioenergy sector setup. 

By conducting BEFS assessments, the organisation works with countries to understand their main biogas needs. 

“We start with the feedstock and feedstock level, so understanding the amount of feedstock that are available and can be used in the country and a whole series of feedstock characteristics including heating values, collection costs and so on.” 

“We then look at the profitability and how the bioenergy option could fare against either other energy uses in the country.” 

By studying the analysis in a map format, the organisation can then tell where the feasible options for bioenergy production can be in the country. For example, in India the group has been looking at rice straw burning. 

“This is an element of a resource that is currently generating GHG emissions. We looked at whether this could be used for bioenergy production of a number of bioenergy types, including compressed biogas.” 

The map can show users the amounts of biogas that could be produced across regions, in this case in the state of Punjab. 

Emphasising that bioenergy solutions are country and case specific, she said that feedstock options need to be assessed in detail and need to consider the agriculture and context setting of the specific country. 

“All logistics around the sourcing of the biomass need to be integrated into the system, considering a biomass supply chain, to enable stable supply of the biomass to the bioenergy production centre.” 

“It’s important that bioenergy gets considered within a broader energy mix. It has a role to play but we need to the enable the system so that it can play its role.”

Farm-based AD

Owner of Apsley Farms in Hampshire Henry du Val de Beaulieu has seen his farm become of the UK’s leading suppliers of biogas. 

By feeding crops such as maize, oats or rye – used as a common ‘alternate crop’ to wheat – into a biogas plant, Apsley Farm is able to produce gas and carbon dioxide (CO2), in addition to fertiliser and compost by-products. 

After getting their first ‘puff of gas’ into the grid by November 2014, the team began to regularly hit full capacity – around 12 times the plant’s initial capacity. 

“In December 2016 we completed our CO2 capture and liquefaction plant and since then we have gradually improved our efficiency by over 10%,” revealed du Val. 

A few years on, the company undertook a sustainability audit on its own farm, achieving a 97% fossil fuel saving on its farm methane. 

“We’ve achieved around 105kg for CO2 per hectare on our own farm, around a quarter of the national average.” 

“In terms of methane emissions our CO2 plant recovery covers any methane slippage which is fed back into the biogas plant.”