Material and Energy valorisation of waste in a Circular Economy

Agro Bio Circular Economy: Developing Sustainable Value Chains from Waste


The University College of Dublin is leading the Agri Bio Circular (ABC) Economy project to reduce greenhouse emissions from agriculture in Ireland by developing new bio-based products and generate energy from biomass wastes available in two Irish counties.

Agriculture is Ireland’s largest indigenous sector forming 7.9 % of total employment. Agri-food exports amounted to approximately 13.6 billion EUR in 2018 (Bord Bia, 2019). Ireland is required to reduce GHG emissions by 30 % on 2005 levels by 2030, but measures to achieve this target are expected to be insufficient as the agriculture currently accounts for 33 % of Ireland’s GHG emissions and is projected to increase due to the removal of milk quotas and expanding animal herd numbers (Joint Committee on Agriculture, Food & the Marine, 2018). One method being pursued by Agri Bio Circular (ABC) Economy to reduce GHG emissions in Ireland is to develop sustainable value chains based on cascading use of biomass to create bio-based products and generate energy.

ABC Economy is led by researchers at the University College of Dublin (UCD) and funded by the Sustainable Energy Authority of Ireland and Department of Agriculture, Food & Marine. This two-year project works with stakeholders to develop new bio-based products and generate energy from biomass wastes available in two Irish counties; Monaghan and Tipperary. The project has initially quantified the biomass available for valorisation in each county. This is followed by a technology review with input from stakeholder workshops to ensure its applicability to rural Ireland. Finally, a full supply chain sustainability analysis will be conducted to examine synergies and trade-offs between using biomass for energy generation and biobased products. This will highlight possibilities to minimise trade-offs by considering the impacts of circular economy principles and cascading systems.

A wide range of biomass available

Manure/litter from livestock and poultry is the most significant biomass available in each county, with ~209kt and ~873kt manure available in a best-case scenario for Monaghan and Tipperary, respectively. This is due to the high amounts of livestock and poultry in each county and their relative manure production. Crop biomass (straw and mushroom) is the next most significant amount of biomass available for valorisation with approximately 30kt and 19kt available in Monaghan and Tipperary, respectively. Spent mushroom compost and mushroom offcuts make up the bulk of biomass available in Monaghan due to the large focus on mushroom growing here. Forestry coverage in Monaghan (approx. 5 % coverage) is well below the national average (11%) and has ~1kt biomass available for valorisation (Department of Agriculture, Food and the Marine, 2019). This compares to Tipperary which is slightly above the national average at 12% coverage and has ~11kt forestry biomass available for valorisation. The key difference in the total biomass available lies in the focus on livestock rearing in Tipperary, compared to poultry farming in Monaghan.

Livestock/poultry manure contains high concentrations of minerals (N & P) as well as organic matter. Anaerobic digestion (AD) or composting is commonly used to eliminate or reduce the risk of pathogens in manure due to high temperatures generated during the processes, producing a safe fertiliser. Biogas derived from AD has high calorific value and can be used as a renewable fuel for electricity and heat production. Poultry litter can also be used as a soil conditioner as it contains higher quantities of N and P compared to other livestock manures and can increase the moisture-holding and nutrient-holding capacities of soils. Poultry litter is also generally easier to collect in higher quantities from poultry housing, compared to cattle manure, making it more simple to apply to land.

Straw and spent mushroom compost have low-medium energy densities, making them unsuitable for energy generation using standard processes (Sustainable Energy Authority of Ireland, 2017). Straw contains various bioactive compounds (policosanols, phenolics, etc.) which have useful nutraceutical properties, e.g. anti-inflammatory, cardioprotective effects, etc. Due to their low concentrations in straw isolating these bioactive compounds may not be economically feasible. However, recovery of these compounds during or before bioconversion of straw to ethanol can improve the feasibility of both processes (Dunford & Edwards, 2010).

Forestry wastes, e.g. small branches and tip-7cm diameter, can be pelletised and combusted for energy generation or potentially mixed with manure to reduce feedstock moisture contents prior to AD. However, gathering forestry wastes in sufficiently high quantities to be economically feasible can be difficult as its removal can adversely impact soil stability and nutrient content. Calcium is present in high concentrations in tree bark offering an option for valorisation alongside energy generation.

Develops sustainable value chains

ABC Economy aims to ensure agricultural and forestry biomasses are collected and utilised in a sustainable manner, i.e. sufficient quantities to be economically feasible whilst also ensure no adverse impacts on the environment by its removal. A cascading system of biomass use can ensure maximum value is derived from biomass whilst reducing adverse environmental impacts. With regards social sustainability, ABC Economy engages with stakeholders to develop sustainable value chains which are relevant for the local bioeconomies of Monaghan and Tipperary. Finally, ABC Economy incorporates holistic life cycle assessment along with market analysis to ensure the true sustainability of the novel value chains developed.

Read more about the ABC Economy Project here: https://www.abceconomy.ie/

Partners: Cre Composting Association of Ireland CLG, Tipperary County Council, and Monaghan County Council.

Funding: Sustainable Energy Authority of Ireland and the Department of Agriculture, Food and the Marine, Ireland (18/RDD/365).

Duration: 2 years

Budget: 224 953 EURO

 

For further details:

Fionnuala Murphy, Assistant Professor University College Dublin*: fionnuala.murphy@ucd.ie

Rosanna Kleemann, Post-doctoral research fellow University College Dublin:  rosanna.kleemann@ucd.ie

*School of Biosystems and Food Engineering, University College Dublin, Ireland

 

References

Bord Bia, 2019. Export Performance & Prospects, s.l.: s.n.

Department of Agriculture, Food and the Marine, 2019. Forest Statistics Ireland 2019, Wexford: s.n.

Dunford, N. T. & Edwards, J., 2010. Nutritional bioactive component of wheat straw as affected by genotype and environment. Bioresource Technology, 101(1), pp. 422-425.

Joint Committee on Agriculture, Food and the Marine, 2018. Climate Change and Sustainability in the Agriculture and Food Sectors, s.l.: s.n.

Sustainable Energy Authority of Ireland, 2017. Bioenergy Supply in Ireland, s.l.: s.n.