(273d) Holistic Assessment of Decarbonization Potential and Their Related Policies for Introducing Anaerobic Digestion in Food Waste Management

According to United Nations Environment Program, 17% of the global food production, corresponding to 931 million tons of food, was wasted in 2019. Among them, 11% is generated in households, which amounts to 74 kg per year.¹ In the United States, 40% of the food produced is thrown away every year, which translates into 99 kg of waste per person and $218 billion worth of lost opportunity.^2,3 Besides its economic significance, food waste has a carbon footprint of approximately 170 million MTCO₂e (excluding landfill emissions and food surplus). Current food waste management involves primarily landfilling, composting, land application, and incineration. Among them, landfills and incineration are the two most popular technologies receiving 75% and 18% of the overall food waste in the US.⁴ These technologies provide low value to the waste generated, and they generate higher emissions in direct (pollutants generated in combustion) or indirect forms (landfill gas). Reducing their contribution is then necessary for mitigating CO₂ emissions. In this context, the Environmental Protection Agency has recommended more sustainable technologies such as composting and anaerobic digestion (AD). However, the products generated by these technologies are not competitive enough (e.g. the production cost of biomethane from AD of food waste is around $22/MMBTU, and the cost of natural gas is ~$7/MMBTU). Thus, developing policies that incentivize their introduction are necessary.

In this work, we compare incentive mechanisms based on their decarbonization potential to promote the introduction of AD technology. Introducing these incentives requires developing a framework that performs a holistic life cycle assessment (LCA) that integrates the emissions of the AD process with the specific geographical conditions. The proposed holistic Life Cycle Analysis (LCA) framework is composed of the following parts:

1. Data collection with specific geographical information. The specific emission factors, the amount of waste generated and the type of management (percentage sent to landfill and type for substitution in system expansion) is collected from open data sources.⁵
2. LCA of AD process. The amount of waste generated, the treatment technologies used for each of them, and the emission factors are substituted into a flexible LCA of the AD process following a system expansion approach where the products and raw materials are substituted. The inventory of the LCA has utilized data from the collaborating company regarding the material and energy flows. Two alternatives for digestate management (landfill disposal and hydrothermal carbonization) and three uses for biogas (upgrading to biomethane, production of electricity and production of hydrogen) are considered.
3. Incentives quantification: The emissions determined by this framework for a plant are scaled up to the entire state with modular plants. The emissions in each of the states have been quantified as Carbon Intensity (CI) score (emission per unit of energy) to be used in the assessment of the incentive’s mechanism. The Low Carbon Fuel Standard (LCFS) mechanism is used for this purpose.

The holistic LCA, apart from being utilized in the incentives’ development, it estimates the maximum decarbonization potential of AD in food waste treatment. An avoidance potential of ~21.8 MMtons CO_2e/y (or 345 gCO₂/kg_waste) and the potential of generating 161 TBTU of natural gas is estimated for the entire US with an average decarbonization cost of ~$128/ tonne_CO2e. The states that benefit more with the new LCFS mechanism are those with the lowest CI Score represented in Figure 1. The incentives introduced with the LCFS mechanism based on LCA with a system expansion approach, reduce the average cost of treating the waste by nearly a half, from $79/tonne_waste to $31/tonne_waste. A comparison of the policy mechanism presented in this work has been performed against the recent Federal Energy Regulatory Order (FERC) 2222 policy, which has shown to favor the introduction of AD in farm-waste treatment facilities.⁶ This FERC-2222 is obtained to have a cost of ~$27/tonne_waste, lower than the one obtained with LCFS mechanism. However, FERC-2222 favors states with less decarbonization potential, which are also the states with more technological development. Thus, an indirect mechanism like LCFS can provide similar economic benefits to FERC-2222 and it can also provide a fairer distribution of the incentives incentivizing the installation of AD facilities is less technological developed regions.

REFERENCES

1. United Nations. Food Waste Index Report, 2021.
2. US Environmental Protection Agency. International Efforts on Waste Food Recovery. 2022.
3. US Department of Agriculture. Food Waste FAQs. 2022. Available in: https://www.usda.gov/foodwaste/faqs
4. Badgett, A. Milbrandt, A. Food waste disposal and utilization in the United States: A spatial cost benefit analysis. 2021. Journal of Cleaner Production, 314, 128057.
5. Explore solutions to food waste. 2022. Available in: https://insights-engine.refed.org/food-waste-monitor?view=overview&year=2019
6. Erickson, E.D. Tominac, P.A. Zavala, V.M. Biogas production in United States dairy farms incentive by electricity policy changes. 2023. Nature Sustainability, 1, 12, 1-9.