TEAGASC PhD Walsh Scholarship

System optimization for the anaerobic co-digestion of slurry with mono-culture and mixed species grass feedstocks

Background:

Ireland has committed to reducing greenhouse gas emissions by 30% by 2030, as mandated by the European Union. Furthermore, ammonia emissions are to be reduced by 1% by 2030 under the National Emissions Ceiling Directive. Concomitantly, renewable energy utilisation should reach 16% of the market. In Ireland, and in many other EU countries, biomethane production by anaerobic digestion (AD) of agricultural feedstocks and residues is a key enabling technology to support the achievement of these targets. Moreover, AD provides the basis to improve grassland and manure management, to increase nutrient recycling and reduce atmospheric losses, while displacing fossil fuel-intensive synthetic fertiliser. While biomethane production is well-established in many EU countries, there is a growing recognition that the AD processes are generally over-dimensioned leading to a sub-optimal economic and environmental performance. AD systems are also subject to unexplained process perturbations. There are two key knowledge gaps that must be addressed in this context: (i) a comprehensive knowledge of the microbes involved in hydrolysis, fermentation and methanogenesis from particular feedstocks, and the optimal environmental conditions for their growth, is required to provide a rational basis for the selection of feedstocks and AD process design not currently available; and (ii) a systematic investigation of the process requirements to optimally produce methane from grass feedstocks has not yet been undertaken, but is required to ensure that reactor stability, loading capacity and methane yields are maximised.

This Walsh Scholarship will address these knowledge gaps through:

(i) the description and optimisation of the microbiology of grass and slurry methanogenesis;

(ii) Optimisation of feedstock mix and composition;

(iii) AD process validation at laboratory- and pilot-scale.

The impact from the project will be a more robust, efficient and environmentally sustainable AD system that, when implemented, will support Ireland and other EU countries in meeting challenging environmental targets.

Back to Research