Rules ‘must change’ on energy from sludge
Water UK's Steve Ntifo, environment and science adviser, and Bruce Horton, policy development adviser, discuss the role of energy from sludge in cutting carbon emissions
Sewage sludge is a by-product of the wastewater treatment process. The amount of sludge generated from the treatment process has risen steadily with progressive implementation of the EU Urban Wastewater Treatment Directive, which was adopted in 1991.
The two main reasons for the increase in sludge production are greater numbers of households and businesses connected to the sewerage network, and the increased level of treatment in order to meet EU and UK regulatory and policy requirements. If energy and climate change had been the serious considerations they are now, there is no doubt that policy decisions and solutions would have been different.
The amount of sewage sludge produced is likely to increase further with additional wastewater treatment to meet the objectives of the Water Framework Directive and directive on priority substances. This is unless principles such as control of pollution at source, polluter pays and cost recovery are properly implemented.
The nutrient and calorific values of sewage sludge, and its contribution to agriculture and energy production, have long been recognised.
In the UK, about 1.4M tonnes of sewage sludge (as dry solids) is produced each year. Some 65% of the sludge is subject to further treatment for and used in agriculture, 19% used in incinerators including combined heat and power (CHP) plants, 6% for reclaiming derelict land, and the remainder for other purposes such as gasification, biogas, cement, compost and aggregate production and landfill. (See Figure 1.)
The water industry uses about 634kWh of energy to treat 1Ml of sewage in England and Wales. This has fallen significantly in recent years as treatment processes have become more efficient. The water industry has a unique opportunity to reduce carbon emissions through the development of renewable technologies such as wind, hydro and CHP. About 14% of total water industry energy use currently comes from renewable sources, about half of which is generated on site. The beneficial contribution of the water industry to climate change mitigation and adaptation will be hampered unless there are policy shifts in the implementation of environmental legislation and targeted policies to encourage energy generation or derivation from sewage sludge through incentives.
The good news is that policy makers in the EU and UK are making progress. A lot is owed to the UK government-commissioned Stern report, which made the economic and political case for climate change.
Water UK supports the principle of target setting presented in the Climate Change Bill. And it considers this will assist in driving action to reduce the use of fossil fuels, which in turn will help mitigate the water industry’s impact on climate change. We welcome the flexibility built into the Climate Change Bill target-setting regime, which requires the Committee on Climate Change to take into account a range of matters when proposing targets.
Combined with the EU commitment to a 20% reduction in CO2 levels by 2020 (rising to 30% with international agreement) and an even more challenging proposed bill in Scotland, this clearly shows the direction of travel.
The Energy White Paper sets out the government’s thinking on some of the tools that are in place or will be needed to move us in the right direction. There is currently no appropriate scheme widely available to the water industry to incentivise carbon emissions reductions through trading.
The EU ETS covers only a very small percentage of the industry’s activities. The proposed Carbon Reduction Commitment is aimed at non-energy-intensive organisations. And it covers only CO2, excluding other greenhouse gases such as methane and nitrous oxide. A sector-specific agreement may be needed for the water sector, embedded in our specific regulatory framework.
Energy can be efficiently generated and used on site, mitigating the need for transmission, and maximising the energy available from renewable sources. But we need to put in place the right frameworks and incentives to ensure the potential for renewable energy generation is fulfilled.
The proposed reform of the renewables obligation sets out possible bands for technologies depending on their maturity and economic need. Our view is that the proposed bands need to be reconsidered if the economic case for sewage gas capture in particular is to stack up. The government should be broadening the obligation and low-carbon subsidies, not deepening certain ones at the expense of others.
As well as the need to consider appropriate incentives for renewable energy generation and ensure the right regulatory vehicle or schemes are in place for the water industry, there are other measures that can be taken.
The water industry is a heavily regulated, energy-intensive industry, with statutory requirements to supply water and wastewater services and to meet stringent health and environmental quality standards. Given the very challenging level of carbon dioxide emission reductions proposed in the draft bill, it is essential that all new European environmental legislation and associated UK regulations, as well as existing legislation not fully implemented, are subject to a robust carbon impact assessment. This would enable the bill to be enhanced, and reflect the national priority to reduce carbon emissions.
Emission reduction targets based on the 1990 baseline would be particularly challenging for the water sector, as EU-driven water quality directives implemented since then have
meant the industry’s carbon footprint has almost doubled in some cases. Reaching
emission reduction targets based on 1990 levels will, at the least, require a more flexible interpretation of the sewage effluent discharge consenting regime.
We also need to work with others to understand the drivers behind the risk-averse approach that companies tend to take on standards – which means we may be unnecessarily over-treating much of our water.
Water efficiency will be key to both mitigation and adaptation – but we need to recognise that this is the responsibility of all of us, not just water companies. A mix of regulation, incentives and voluntary action will be needed, along with a regulatory and incentive driven regime that encourages the more efficient use of water.
The Directive and Regulations on Integrated Pollution Prevention and Control in their current form make it more difficult and economically questionable to recover energy from sludge for example through biogas generation.
It would make economic sense to generate biogas from sewage sludge provided the total power requirement was less that 3MW, in which case such a plant will be subject to Waste Management Licence Regulations instead of Pollution Prevention Regulations.
If the power threshold goes above 3MW, the regulatory burden and policy cost make it less attractive. And, there is the potential to lose this useful renewable energy. The answer may be as simple as changing the law or adopting a pragmatic enforcement position, which should not be beyond our wits.
Policies and regulations affecting sewage sludge need to change if we are to get the best from a valuable resource that many have considered to be waste. Existing technologies that have delivered so much to date should receive additional support from current and future policies aimed at tackling climate change.
Business should be given long-term policy frameworks to develop new and cost-effective technologies to meet the challenges of climate change. Where policies and regulatory regimes are barriers to development of options needed by industry, policy makers must work with the supply chain to find better solutions.
Traditional solutions and blinkered strategies will not do for the future if the water industry is to reduce its energy consumption and climate change impact. Policies such as resource productivity and recycling, polluter pays, cost recovery from polluting sectors, and pollution control must be properly implemented to produce better outcomes for the environment and society.
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