Renewable energy, anaerobic digestion, sustainable development


    Global warming, which means the increase of the average global temperature of the Earth’s climate system, has far-reaching negative impacts on the human population and ecosystems and is the biggest challenge to achieving sustainable development. The predicted negative effects of global warming include increased unpredictability of the weather and climate; dramatically increased severity, scale, and frequency of extreme weather events such as storms, heatwaves, droughts, and flooding; melting of ice sheets, which contributes to rising sea levels; changes to regional climate; food and freshwater availability; and biodiversity loss.


    Human activity is the dominant driver for the observed warming in the industrial era, and the largest anthropogenic contributor is the emission of greenhouse gas such as carbon dioxide. Carbon dioxide from the burning of fossil fuels and industry is the largest source of greenhouse gas, accounting for about three-fourths of total global emissions.


    Many impacts of global warming have already been observed, such as declines in the Arctic sea ice extent, extreme weather events, and rising sea levels to name a few. Some of these impacts are also already visible in Ireland: increased number of warm days and decreased number of annual frosty days, increased average annual national rainfall (60mm higher in the period 1981 to 2010 than the period 1961 to 1990), increased river flow, increased mean annual sea surface temperature (1.0°C higher than that during 1961-1990, as measured at Malin Head, Co. Donegal), a sea-level rise of 1.7cm per decade.


    The impacts of global warming can reach levels of irreversibility if global warming exceeds ‘tipping points’, beyond which certain impacts become irreversible even if temperatures are reduced. To avoid some of the irreversible impacts, keeping global warming below 1.5 °C compared to pre-industrial levels is needed, as emphasized by the Intergovernmental Panel on Climate Change (IPCC). We have to reduce global carbon emissions by 45% from 2010 levels, by 2030 in order to reach the carbon neutrality target by 2050. We only have a limited window to limit global warming to 1.5 °C, which would require rapid and unprecedented changes in all aspects of governments, industries, and societies.

    Global Temperature July


    EU and Ireland’s effort to curb global warming: the role of renewable energy


    The European Union has set binding targets to curb global warming by reducing greenhouse gas emissions, including reducing greenhouse gas emissions by at least 40% below 1990 levels by 2030.  Increasing the use of renewable energy, i.e., energy from renewable sources, is an important part of the package of measures needed to achieve these goals. The European Union is aiming at increasing the share of renewable energy to at least 32% of EU energy use by 2030. Each Member State is required to submit a 10-year National Energy and Climate Plan (NECP) to set out its contribution to these targets and how to reach these targets.


    According to Ireland’s draft NECP, Ireland can expect renewable energy share of 15.8 – 19.2% by 2030 (without additional measures) and 23.7 – 27.7% with additional measures, which are less than the required target of 31% (results from Regulation (EU) 2018/1999 on the Governance of the Energy Union and Climate Action). The final NECP will be a binding plan and missing the target may lead to fines. On the other hand, Ireland is on track to miss its 2020 renewable energy targets of 16% and ranked 26th out of 28 member states in the EU (as of 2019) in terms of its progress towards renewable energy targets. Transformative changes in industries and societies in terms of energy utilization are needed to achieve Ireland’s goals.


    Renewable energy from anaerobic digestion


    Anaerobic Digestion is a process where several groups of microorganisms break down organic non-woody components in the feedstock in the absence of oxygen. Anaerobic digestion produces biogas and digestate. Digestate contains nitrogen and phosphorus and can be used as fertilizer. Biogas mainly consists of methane, the same chemical compound contained in natural gas and can be used directly as fuel for combined heat and power engines or upgraded and injected into the natural gas network. Common feedstocks for anaerobic digestion include wastes such as slurry and manure from cattle, poultry, and pigs, domestic food waste, organic wastes and wastewaters from food and beverage processing industries, and grass and maize, etc 


    Anaerobic digestion is a source of renewable energy and can reduce carbon emissions by generating bioenergy from carbon. This can replace fossil fuel with renewable biomethane. Biomethane is a product certified by Gas Networks Ireland with standards equivalent to natural gas for grid injection.  

    In addition to the provision of renewable energy, anaerobic digestion also facilitates reduced carbon footprint, greenhouse gas reduction, sustainable waste treatment, nutrient recycling, soil carbon sequestration and CO2 separation for reuse in industry, at dedicated RenewablCentres. 

    There is no shortage of potential indigenous anaerobic digestion feedstock in Ireland: roughly 7 million cattle, 5.2 million sheep, 1.5 million pigs, and 11 million poultry, together with waste arising from crop farming industry and households (as of 2016)It is predicted that carbon emission savings of up to 0.7 Mt CO2e/year by 2030 and 2 Mt CO2e/year by 2050 can be achieved using anaerobic digestion to produce biogas. 

    To achieve the aforementioned carbon emission savings, methane production of around 300 million m3 by 2030 and 1200 million m3 by 2050 is required. Assuming each anaerobic digestion plant produces methane at a rate of 11.4 Nm3/hr (0.1 M m3/year)this would require the establishment of around 300 anaerobic digestion plants by 2030 and 1200 by 2050, which could be an achievable goal if we look at the development of anaerobic digestion in other areas of Europe.  


    More than 17,400 biogas plants are producing 18,400 million m3 biogas (662 PJ) in Europe (as of 2015), making EU the world leader in biogas electricity production. In the EU, Germany has the highest biogas production of 9,200 million m3  with around 8,000 installations. Biogas productions in other countries are approximately 2,600 million m3 in the UK (500 plants)2,200 million m3 in Italy (1000 plants), and 260 million m3 in Belgium and Poland. Northern Ireland has also seen significant developments in the anaerobic digestion sector: 24 new installations have been commissioned since 2015 and 103 more approved or under construction as of 2017. However, anaerobic digestion in Ireland is under-developed with less than 10 anaerobic digestion plants operating in Ireland, producing 64 million m3 methane (2.3 PJ, 1.5% of natural gas consumption) as of 2015. There is great potential for the development of anaerobic digestion in Ireland, which would require encouraging policies from the government and commitments from the industry. 

    AD Plants in Europe & Biogas Energy Production Graphs

    Reference: Scarlat, N., Dallemand, J.-F., Fahl, F., 2018. Biogas: Developments and perspectives in Europe. Renewable Energy. 129, 457-472

    WEW Engineering’s commitments

    WEW Engineering is currently conducting an innovative research and development project aimed at the provision of automatic monitoring and control systems, to optimize the performance and commercial management of integrated unit operations at Renewable Centres. Further research areas include the investigation of the feedstock marketrelevant regulations, and additional aspects relating to anaerobic digestion.  

    WEW Engineering is committed to optimise bioenergy recovery and to apply sustainable engineering technology in the interest of climate change, following the recommendations of the Paris agreement. 

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