BETA-EBM · Biomass Energy Technology Assessment - Environmental Burden Minimisation

Biomass Energy Technology Assessment - Environmental Burden Minimisation

Comprehensive Project Overview The underpinning motive of this MC-IoF (Bioenergy Technology Assessment – Environmental Burden Minimisation, BETA-EBM) has been to promote environmentally savvy AD operation, beyond its longstanding role in waste volume reductions and biogas recovery. The specific training elements of the project provided the Fellow expertise in evaluation and improvisation of the systems scale environmental performance of bioenergy installations, focussing on Anaerobic Digestion (AD) technology. A major accomplishment of this project has been development of a ‘proof of concept’ in enhancing resource and environmental efficiency of AD operation through inter-continental collaboration between the Energy and Environment Technology Development at the Energy and Resources Institute, India (outgoing host) and the Centre for Environmental Sciences in the Faculty of Engineering and the Environment at the University of Southampton, UK (reintegration host). Essentially, successful completion of the two-year project facilitated skills development of the Fellow in evaluation of the current practice in bioenergy assessment by ascertaining: i.) the environmental impact/s from process enhancement via acidification and methanation for utilising urban domestic waste as substrate in a small-scale AD system; ii.) the potential for environmental burden reduction using process enhancement; iii.) the potential for environmentally savvy, distributed AD installation for community and industrial deployment in Europe (in terms of resource-efficient installations, fulfilling systems scale environmental compliance). Community-scale, high-tech, bioenergy plants are deemed integral to sustainable urban metabolism – for both local waste management and provision of replenishable bio energy. Addressing this demand the project developed shared knowledge through research training and networking at an international forum. The results arising from this work have paved scope for forward-looking and multidisciplinary applications, drawing interests from the following two broad categories of stakeholders – i.) Sustainability science (primarily researchers involved in urban waste management, renewable bio energy and environmental management); ii.) Socio-economic transition (including government bodies/planners and civil societies/community groups involved in building resilient and self-sufficient local communities through promotion of waste- and energy-grid independence). The suggested study outcomes from experimental work conducted during the project offer a win-win for both bioenergy production and environmental burden minimisation; facilitating numerous pathways in addressing the environmental issues in municipal/industrial biowaste valorisation for energy self-sufficiency. This has been long time overdue towards ensuring a sustainable pathway for fostering environmental best practice in AD operation – useful to both AD operators commercially and to the community at large. The experimental set up During the outgoing phase of the project a portable sampling kit was developed for estimation of key environmental burdens to air (pollutants and greenhouse gases), mainly from land application of digestate (the residual biomass obtained post AD) (Figure 1). This experimental set up was utilised for conducting a number of studies, first to obtain the baseline emissions profiles of pollutants (NH3, SO2) and greenhouse gases (N2O, CH4) from digestate land application, followed by iterative evaluation of different grey-water reutilisation and digestate management strategies, including response to alterations in feedstocks, effluent recirculation, post-methantion and seasonal variations. The results and their socio-economic impacts Some interesting results from the repeat experiments, conducted in Year 1, have been obtained. For instance, results from the first round experiments on evaluation of the responses to air emissions (pollutant and GHGs) from AD feedstock alteration, digestate post-methanation and soil incorporation have provided insight into development of some best practice for environmental burden minimisation from digestate land application. Further, evaluation of the combined effects of varying effluent recirculation (25%, 50%, 75% v./v.) and digestate land application on the altered environmental burdens has facilitated development of an integrated AD system - coupling the features of two community-scale digesters processing organic fractions of municipal solid waste (OFMSW) – a two-stage wet-AD (>90% moisture) with a single-stage dry-AD (60-85% moisture). Our study has shown interesting trade-offs of practical implications in using this integrated approach. Increasing the effluent recycling from 25% to 50% seems to positively affect the integrated system as – wet-AD: reduced effluent discharge; dry-AD: enhanced biogas yield with minimal increase to the digestate NH3 emissions. However, increasing the effluent recycling to 75% negatively affected performance of dry-AD: the biogas yield reduced steeply over the 6-day monitoring period; digestate NH3 emissions increased drastically. This outweighed the environmental burden minimisation potential for the 75% nutrient recycling option despite its high effluent reduction potential from wet-AD. The results obtained so far have provided primary data towards development of some best practice in AD operation, including handling of digestate post AD as soil amendments, optimal reutilisation of effluent and nutrients through process modification. The preliminary results generated over this 2-year period are of relevance to both industrial/commercial clients and researchers in developing integrated bioenergy solutions. This is expected to re-define the green credentials of AD, thereby securing its long-term viability as an alternative, renewable energy technology, essentially making it equally competent with the likes of solar, wind/tidal and geo-thermal. Contact details MC Fellow: Dr Abhishek Tiwary (A.Tiwary@soton.ac.uk); Scientist-in-charge: Prof Ian Williams (I.D.Williams@soton.ac.uk). Corresponding address: Centre for Environmental Sciences, Faculty of Engineering and the Environment, Lanchester Building, University of Southampton, Highfield, Southampton, Hampshire, SO17 1BJ, UK.

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