LimeLight: Agricultural Waste to Clean Energy and Sustainable Fertiliser

The LimeLight project explored how agricultural waste could be transformed into valuable products that support both clean energy and sustainable farming. Led by Queen’s University Belfast and AFBI, with support from United Renewables, Colloide, and Encirc, the project focused on integrating two innovative technologies: ammonia recovery and biochar production.

Using lime and low-grade heat, the team developed a process to strip ammonia from anaerobic digestate—a byproduct of biogas production. This recovered ammonia was concentrated into a liquid fertiliser or cleaning product. The remaining digestate was then dried and converted into biochar, a carbon-rich material with long-term storage potential and soil-enhancing properties.

The project also investigated using waste lime from the glass and cement industries to reduce costs and improve sustainability. By combining ammonia recovery and biochar production, the team created a circular system that reduced emissions, improved nutrient management, and supported the decarbonisation of agriculture and construction.

Life Cycle Assessment and techno-economic modelling confirmed the environmental and financial benefits of the integrated system. The project showed that Northern Ireland’s livestock sector could produce over 6,000 GWh of biomethane and 420,000 tonnes of biochar annually—equivalent to removing 777,000 tonnes of CO₂ from the atmosphere.

LimeLight laid the groundwork for a full-scale demonstration plant and offered a scalable solution for rural communities. It supported policy goals around net zero, green growth, and circular economy, while creating new opportunities for jobs, innovation, and sustainable development.

Partners:

Renewables United