A Life Cycle Assessment Approach to Biosolids Management

In the wastewater treatment industry there is a gap between the financial analysis and the environmental impact analysis that municipalities can utilize to make sustainable decisions. A Life Cycle Assessment (LCA) provides a holistic, “cradle-to-grave” analysis within the defined system boundaries, allowing decision-makers to meet the “triple bottom line” goals. LCA is a unique tool that provides a means to fill this gap and quantify the environmental impacts, assisting a facility in selecting the appropriate technology to manage its biosolids. In addition to the traditional life cycle cost comparison, an LCA compares carbon footprinting, eco-toxicity, and green-house gas emissions, among other environmental impact categories of importance to a particular facility. It provides an accurate accounting of different, often conflicting, environmental parameters. For example, LCA would be a useful tool to quantify impacts in the case of membrane technology for wastewater treatment, which provides higher effluent quality but consumes significantly more energy than an activated sludge process.The case study focused on comparing different biosolids disposal alternatives which include land filling, land application and incineration. The model defines the system boundary to account for emissions to air, water, and land. The operating costs include resource consumption, energy usage, electricity from various sources and trucking impacts for the different biosolids management alternatives. The environmental impacts of each of the treatment technologies were aggregated into categories such as global warming, greenhouse gas emissions, acidification, utilizing the SimaPro software package to implement the IMPACT 2002+, Eco-Invent and IPCC (Intergovernmental Panel on Climate Change) evaluation methodologies.The results from the study helped understand the environmental burdens for each alternative based on energy and material inputs as well as the importance of selecting a candidate methodology. It also highlights the significance of transportation choices for biosolids management in terms of in energy consumption, global warming and human toxicity burdens.