Decarbonisation Technology - August 2024 Issue

Waste to revenue for meeting decarbonisation goals Technology enhancements that recover energy from waste provide multiple benefits, including cost reductions and the creation of new revenue streams

Dave Swerdlyk Veolia Water Technologies & Solutions

W astewater treatment plants (WWTPs) can play a larger role in contributing to decarbonisation goals. Today, more technology options are available for them, which can ultimately lead to reductions in greenhouse gas (GHG) emissions. However, the options are not solely driven by climate- related benefits. Also in the mix are substantial economic returns, including cost reductions and the creation of new, long-term revenue streams to support operations beyond traditional user rate financing. The strategies for achieving these results primarily revolve around the management of organic waste and sludge, the latter a byproduct of wastewater treatment. When these materials are landfilled, they decompose over time and release GHG emissions, primarily carbon dioxide (CO 2 ) and methane. CO 2 , the predominant GHG from human activities, is the largest contributor to global warming. Methane ranks as the second most prevalent human-made GHG, responsible for approximately 16% of global emissions. Notably, methane concentrations in the atmosphere have more than doubled over the last two centuries. The US Environmental Protection Agency (EPA) notes that methane is more than 28 times more potent than CO 2 at trapping heat in the atmosphere. The EPA also identifies municipal solid waste (MSW) landfills as the third-largest source of human-related methane emissions in the U.S., highlighting the critical role of waste diversion strategies. This is where WWTPs can make a difference. By treating sludge and organics with anaerobic digestion (AD) technology, WWTPs can reduce the volumes of waste destined for

landfills, reducing trucking and disposal costs, lowering GHG emissions, and extending the life of these landfill sites. The added value of AD is the opportunity for resource recovery. The AD process generates methane-rich biogas as a byproduct, which can be captured and utilised in multiple ways. One method involves using it to power a combined heat and power (CHP) system, generating both electricity and thermal energy for on-site use. An even more profitable approach involves upgrading the biogas into renewable natural gas (RNG) and injecting it into a commercial natural gas pipeline. This allows the RNG to be transported and sold in the energy market, where a higher payback can be realised as it can be monetised in a variety of transportation, heating and commercial applications. The sale of RNG provides a commodity value. Additionally, under the Federal Renewable Fuel Standard (RFS) Program, RNG producers can earn renewable identification number (RIN) credits. These credits, used to track renewable fuel production and usage, can be traded on the market and serve as the currency of the RFS program, offering another revenue stream. Companies that do not meet the mandated renewable fuel amounts (referred to as ‘obligated parties’, such as petroleum refiners and importers of refined fuels) must buy these credits to meet regulatory requirements. In addition to reducing GHG emissions from landfills, converting sludge and organic waste into RNG is a beneficial circular economy practice that offsets the use of fossil fuel- derived natural gas, lowering the carbon footprint of energy production.