Maximizing the Value of Biogas Through Consideration of Alternative Uses


  • Matt Van Horne, Bryan Lisk, Micah Blate - Hazen and Sawyer

One biogas utilization approach is a combined heat and power system, such as the one pictured here. This established technology has 70%-80% utilization efficiency and typically generates 20%-40% of plant energy usage.

New biogas utilization technologies and evolving renewable energy markets are presenting new opportunities for biogas utilization, an example of which can be found in Raleigh NC. The city is using biogas to power the City's bus fleet, among other uses.

Biogas can also be conditioned to “pipeline quality” and injected into the natural gas supply pipeline.

The EBAT tool helps utilities easily model outcomes for multiple energy optimization scenarios and understand range of economic outcomes for multiple alternatives.

An EBAT analysis for a large utility in Virginia showed that CHP has the highest plant purchased power offset potential.

An EBAT model for a California utility showed that both CHP and natural gas could offer the utility economic benefits.

Our model for a third utility showed that CHP offered more predictable outcomes and less overall risk than pipeline injection.

Biogas produced from anaerobic digestion has long been used for power generation and process heating. However, new biogas utilization technologies and evolving renewable energy markets (i.e. renewable fuels markets, renewable energy markets, low carbon fuels, etc..) are opening up new alternatives to conventional biogas utilization methods. This technology growth, combined with uncertain future energy markets/regulations, has significantly widened the range of economic outcomes and the long term feasibility for all biogas utilization technologies. Accounting for this range of future conditions can be a significant challenge for wastewater utilities when evaluating long-term biogas utilization strategies. Failure to account for the full range of future plant, regulatory, and market conditions can result in inaccurate assessments of long term benefits and risks.

Beyond the technical considerations for the various utilization approaches, there are a significant number of market and regulatory conditions that must be considered for each utilization alternative. To capture the full range of long term outcomes, an Energy Balance and Analysis Tool (EBAT) has been developed. EBAT models the energy projection benefit for a wide range utilization technologies under multiple long term future conditions including high and low market conditions, high and low plant growth, and impacts from co-digestion.

The EBAT model is used to model the range of projected future market and plant conditions and the results enable wastewater utilities to make more informed decisions on their long term biogas utilization strategies. Some of the currently available biogas utilization approaches include combined heat and power systems, biogas to vehicle fuel, and biogas to natural gas. The EBAT tool has helped utilities of various sizes determine the highest value digester gas utilization approach.

While recovery of digester gas can offer utilities several opportunities to cut energy costs or generate revenue, looking ahead, we now sit at the crossroads where recovery of cellulose, high value carbon, bioelectrochemical products, rare earth elements and plasmids represent the next generation of resource recovery.

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Horizons Fall 2017 (pdf)

Horizons showcases significant water, wastewater, reuse, and stormwater projects and innovations that help our clients to achieve their goals, and can help you achieve yours. Articles are written by top engineers and process group leaders, demonstrating and explaining the beneficial application of a variety of technologies and tools.

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