Opportunities and challenges of developing anaerobic digestion
01 September 2014
Authors: Kevin Fitzduff & Morgan Burke, Stream BioEnergy
Anaerobic digestion (AD) is a sustainable form of renewable energy production through a naturally occurring process in which micro-organisms break down biodegradable material in the absence of oxygen in an enclosed system. The process produces a methane-rich biogas and a nutrient-rich fertiliser known as ‘digestate’.
All organic material except wood can be used in the AD process. Feedstocks for biogas production include domestic and commercial organic waste (MSW), industrial organic waste from the food- and beverage-processing industry and sewage sludge from wastewater treatment plants, and organic wastes from the agricultural sector.
BENEFITS OF ANAEROBIC DIGESTION
AD is a proven and efficient technology that will deliver multiple energy, climate, environmental, societal and economic benefits. It can help Ireland meet a number of important EU and national policy commitments, as well as contributing towards achieving national recycling targets. Rather than continuing to discard organic waste to landfill and landspreading, AD can be used to produce renewable energy from this waste and to generate a fertiliser product. It can therefore make a significant contribution to the management of organic materials in Ireland.
Energy sourced from AD will play an important role in helping to achieve Ireland’s EU Renewable Energy Targets for 2020, as well as diversifying the national fuel mix and reducing the country’s reliance on imported fossil fuels. AD also has an important role to play in the fight against climate change. By diverting organic waste from landfill and landspreading, AD can reduce uncontrolled emissions of methane to the atmosphere. Replacing fossil fuels with renewable energy generated in this manner also reduces greenhouse gas emissions.
AD not only recovers the energy from organic waste, but it also produces a nutrient rich digestate that can be suitable for use as an organic soil conditioner or biofertiliser for agricultural and horticultural purposes thus reducing reliance on artificial fertilisers that are becoming increasingly expensive to manufacture.
The nutrients contained in digestate are more amenable to plant uptake than other organic fertilisers and, thus, its use has water quality benefits as it reduces organic pollution potential as well as reducing risk of spreading microbial contamination.
There is massive potential for a new rural industry generating biogas from farm waste in AD plants, which will help address the challenge of converting to a low-carbon agricultural sector going forward. Furthermore, there will be a substantial increase in the volume of agricultural organic wastes generated due to the planned increase in output from the Irish agri-food and fisheries sector as part of the Government’s Food Harvest 2020 target. AD would support sustainable development in rural areas and provide diversification and stability of income for rural families, as well as attracting young people back to farming.
Realisation of the full potential for AD in Ireland could result in a capital investment of up to €1.4 billion to the economy. It would also generate much-needed employment by creating thousands of jobs in engineering, construction, manufacturing and other local professional services. This is far in excess of what could be created through other renewable energy technologies. There would be new business opportunities for sectors that can provide services to the AD industry and the development of the AD sector would also promote more balanced regional economic development as revenue from the plants is likely to be spent locally.
INITIATIVES AND DRIVERS FOR DEVELOPMENT
There are many factors influencing the market for AD in Ireland, ranging from new legislation to Government policy drivers and economic initiatives. EU legislation such as the Waste Framework Directive (2008/98/EC) and the Landfill Directive (1999/31/EC) are important factors driving interest in AD in Ireland. New national legislation such as the Commercial Food Waste Regulations (SI 508 of 2009) and the Household Food Waste Regulations (SI 251 of 2013), if properly implemented and enforced, will promote the segregation of food waste at source – thus increasing the amount of organic waste that will require biological treatment. The potential of AD is also recognised in Irish national waste policy.
Compared to most EU countries, the AD sector is severely under-developed in the Republic of Ireland. Apart from a low number of AD plants built at industrial facilities including wastewater treatment plants to process sewage sludge, there are only four agricultural AD plants in operation on farms which are of relatively small scale. There are no large-scale AD plants in operation to process the organic fraction of municipal solid waste or industrial waste.
In contrast to this, a stimulating regulatory and financial framework, driven by high oil prices and a positive public opinion towards renewable energy, have had a big influence on the successful and widespread development of AD facilities in many other European countries. This demonstrates that AD technology is well proven and implemented in Europe as a viable treatment technology for organic waste.
The main reasons for the lack of AD infrastructure rollout in Ireland have been a combination of regulatory uncertainty and an ongoing lack of economic incentive. The publication of the Government’s new national waste policy, A Resource Opportunity, in July 2012 has brought some stability to the waste market after a prolonged period of uncertainty.
However, the main development constraint is a lack of economic viability to developers and investors and improved fiscal incentives are urgently required to enhance the attractiveness of AD for investment.
COMPARISON OF EUROPEAN BIOGAS POTENTIAL
The Cross Border Bioenergy Working Group on biogas technologies has prepared an analysis of each European country for its biogas potential based on a number of criteria: basic country data, energy policy, feedstocks, economic conditions, market environment, regulation, project financing and readiness for uptake. The results of the study are shown in Figure 1.
It can be seen that Ireland has the lowest score in Europe by a long way. Of the eight areas identified by the Cross Border Bioenergy Working Group, the most important is the economic conditions which are driven primarily by the renewable energy support mechanism in each country.
RENEWABLE ENERGY FEED-IN TARIFF
The current Irish electricity support price (REFIT) tariffs for AD are disappointingly low and do not provide a sufficient subsidy to support the economic case for the widescale deployment of AD facilities in Ireland.
For example, the REFIT price for an AD plant (with CHP) generating more than 500kW is €136MW/h. The following table compares this level of support with selected feed-in tariffs from other European countries.
|Country||Total Price for Electricity from Biogas € per kw|
|Germany||€0.18 – 0.28|
|Italy||€0.22 – 0.28|
|United Kingdom||€0.18 – 0.25|
|Northern Ireland||€0.22 – 0.28|
|Austria||€0.18 – 0.21|
|France||€0.16 (30% capital grant)|
|Latvia||€0.15 – 0.20 (linked to gas price)|
|Czech Republic||€0.16 – 0.18 (up to 30% capital grant)|
|Republic of Ireland||€0.13 – 0.15|
This table demonstrates that the current REFIT tariffs for AD in the Republic of Ireland are not only low, but are in fact amongst the lowest in Europe. Countries in which development of AD has been most widespread are Italy, Germany (with over 6,000 plants installed) and the UK.
The AD industry has flourished in the UK over the last five years, with over 100 plants now in operation beyond the water sector and hundreds more awaiting planning permission. It is noticeable that these three countries all have average prices for electricity generated from biogas in excess of €0.20 per kWh. Countries which have average prices of between €0.15 and €0.20 have all seen moderate development of AD plants, while those with average prices below €0.15 have seen little development.
In our nearest neighbour, Northern Ireland, the total price paid for electricity from an AD plant generating more than 500kw is approximately £196/MWh (€225/MWh) (inclusive of the ROC price, the price paid for electricity, and the climate change levy exemption credit), which is 65% higher than that received for generation from a similar scale facility in the Republic of Ireland.
The improved electricity tariffs in Northern Ireland have resulted in a significant growth in AD development in the country over the last few years, with over 130 planning applications submitted, mostly for on-farm systems processing slurries and grass silage. This is clearly a threat to the development of AD in the Republic of Ireland, as waste may flow across the border to meet the feedstock requirements of these plants.
The evidence from other European countries highlights the need for a support tariff of at least 20c/kWh in order to incentivise significant AD development. Small-scale AD plants producing energy from only agricultural waste in particular will need a higher tariff to offset the lack of gate fee revenue to these plants and to encourage uptake by the farming community.
RENEWABLE HEAT INCENTIVE
In addition to improved REFIT levels, a renewable heat incentive (RHI) similar to that recently introduced in the UK could incentivise the direct injection of upgraded biogas into the gas grid for use as a natural gas substitute to help achieve our renewable heat and transport targets. Austria, France, Germany, Italy, Luxembourg, Netherlands, Norway, Sweden, Switzerland and the UK all provide a mechanism for biogas injection to the gas network.
The provision of a renewable incentive for grid injection of biogas could cost less to subsidise than the current REFIT tariffs for electricity, and still be more attractive for AD plant operators where the plants are in close proximity to the gas network. By providing a tariff in line with that offered by other European countries, the Government could reduce the subsidy cost for a plant and encourage more development.
Now more than ever, there are broader national reasons for supporting the development of AD in Ireland including job creation, environmental benefits, energy security and redirection of money currently spent on fuel imports to boost our local economy. On a local level, it makes sense to recycle our waste and to grow our own energy supply, sustaining much needed employment in the process. If the correct economic conditions prevail, in line with other European countries, a new industry with huge potential could develop in Ireland.https://www.engineersjournal.ie/2014/09/01/opportunities-challenges-developing-anaerobic-digestion/https://www.engineersjournal.ie/wp-content/uploads/2014/08/Anaerobic-1024x684.jpghttps://www.engineersjournal.ie/wp-content/uploads/2014/08/Anaerobic-300x300.jpgChemIreland,renewables