Deriving Energy from Waste
IT MAY LOOK LIKE GARBAGE TO THE AVERAGE PERSON, BUT THERE CAN BE A TREMENDOUS AMOUNT OF ENERGY LOCKED UP INSIDE THAT WASTE. CONVERTING THAT ENERGY IS NOT ONLY SUSTAINABLE, IT SAVES SIGNIFICANTLY ON OPERATING COSTS.
One of the greatest challenges facing the development and expansion of urban living is the issue of waste removal and management. Whether it is coping with over-capacitated landfills in developed countries, or handling the mass influx of people from rural areas into cities in developing countries, one of the common core issues is dealing with waste.
Clearly, it is difficult to have a discussion about long-term sustainability without a serious examination on how to reuse waste. All too often, waste – be it garbage, sewage, food or industrial – is disposed of in a landfill, where we can wait centuries (literally) for it to decay. There has to be a better solution – and there is.
Today private and municipal utility service providers around the world are developing new solutions for energy resource recovery and sustainability. With increasing efficiency, the world is learning how to turn yesterday’s waste into today’s usable energy.
“Waste-to-energy programs offer a comprehensive approach to achieving many sustainability goals,” said Paul Street, Director for Sustainable Solutions, Black & Veatch. “This is important, especially in light of increasingly stringent regulatory requirements governing emissions and water quality in many regions of the world, and public demand for greater utilization of resources.”
However, challenges to the technology, particularly in the area of capital investment costs, must be overcome to drive widespread adoption of the practice. Though the economics of waste-to-energy projects vary by region, all operators must address their most critical sustainability issue – economic sustainability.
BIOSOLIDS FOR ENERGY IN THE UK
In 2010, the United Kingdom passed legislation increasing the landfill tax £8 per ton each April through 2014, doubling the fee to £80 per year. Further, the EU Landfill Directive requires member states to cut the amount of biodegradable municipal waste they send to landfills to 50 percent of 1995 levels by 2013 and 35 percent by 2020.
“Given significant economic and regulatory pressure to more effectively manage resources, and the billions of pound/sterling potentially lost through inefficiency each year, projects like United Utilities new sludge treatment scheme at Davyhulme Wastewater Treatment Works in Manchester, England, can play a beneficial role in achieving these targets,” added Street.
The Davyhulme project is one of the largest design-and-build biosolids-to-energy projects in the world and is being developed to increase the works capacity and improve the quality of treated sludge. It will produce both fertilizer for agriculture and gas that will be converted to electricity.
The project will provide a central sludge processing facility, and upon its completion, the works will also receive imported raw sludge and imported raw liquid sludges from within and outside of the city.
Treated sludge will be recycled as a soil conditioner (fertilizer) to agricultural land or in part for flexibility by incineration at United Utilities’ Mersey Valley Processing Centre. The gas will pass through cleanup equipment to the 12 MW (electrical) combined heat and power engines, producing enough energy to use on-site or for export to the national electricity grid.
Overall, the facility is anticipated to generate more than 31 gigawatt-hours of extra electricity per year, save more than 16,000 tons of CO2 emissions and save over £3 million annually through reduced energy costs and better sludge management.
WASTE-TO-GAS IN NY
Balancing resource and economic sustainability goals can be a particularly challenging task in the United States, where historically low natural gas prices impact stand-alone economic comparisons between landfill disposal, waste-to-gas and other technologies. However, regulatory standards and public policy goals are playing a role in determining the adoption of new technologies.
For instance, New York City has launched an initiative called PlaNYC, which calls for a 30 percent reduction of citywide greenhouse gas emissions and energy consumption by 2030. To help achieve this goal, the New York City Department of Environmental Protection (NYCDEP) is converting the main sewage pumps and process aeration blower systems at its North River Wastewater Treatment Plant to increase use of waste-to-gas resources.
“Given the new landscape under which wastewater treatment plants must operate, there is a critical need to evaluate energy efficiency and production opportunities,” said Anthony Fiore, NYCDEP Chief of Staff to the Deputy Commissioner. “As such, DEP is looking at a variety of practices to harness the benefits of waste-to-gas technology.”
Currently, diesel is the primary fuel stock powering the main diesel/biogas sewage pump and aeration blower engines at the North River Plant. The system requires approximately 10 percent diesel even when utilizing digester gas. The existing 10 engines will be replaced with a cogeneration system using biogas obtained via enhanced gas recovery processes and cleaner-burning natural gas to increase the system’s efficiency. This will reduce the plant’s operating costs by eliminating the need to purchase diesel fuel and will help contribute to the PlaNYC goal.
Kyriacos Pierides, Black & Veatch Client Services Manager, noted, “Looking at the trends for greenhouse gas regulation and energy reduction requirements, we expect that both existing facilities and future waste treatment designs will seek to increase the use of waste-to-energy technologies to meet their operational and environmental goals.”
Recycled Methane Gas Produces Fertilizer
Another example of the move towards sustainable energy practices is the Morris Forman Water Quality Treatment Center, owned by the Louisville and Jefferson County (Kentucky) Metropolitan Sewer District. Utilizing recycled methane gas from its wastewater treatment operations as the primary fuel for its dryers, the center produced and distributed 28,210 tons of treated biosolids fertilizer to bulk agriculture, fertilizer blenders and local retail outlets.
According to its 2010 Annual Report, as a result of its comprehensive approach to resource management, less than 0.5 percent of all solids processed at Morris Forman in 2010 were sent to the landfill. For the 12-month period, this solution generated savings of approximately $663,500 in landfill costs, with an additional savings of more than $750,000 realized by using the recycled methane to power the facility.
“Making advances in working with all forms of waste-to-energy technologies provides constant sources of renewable energy production,” added Street. “Whether it’s food waste-to-energy projects, municipal waste recycling and conversion, or other biosolids conversion, by avoiding landfills and harnessing the inherent energy resources, plant operators are reducing the amount of fossil fuel required to dispose of waste and reducing capital and operational costs.”
Story by Patrick MacElroy, Black & Veatch