Development of a Cost Optimization Algorithm for Food and Flora Waste to Fleet Fuel (F4)

As cities strive for more sustainable transportation systems, many are considering renewable fuels for fleets. Biogas has several advantages as an alternative fuel. Composed primarily of methane, it can be cleaned for use in natural gas vehicles or burned in a turbine/engine to generate electricity for electric vehicles. Biogas can reduce air pollutant emissions from fleet vehicles; in addition, if wastes are used to produce the biogas in digesters, the problem of urban wastes is reduced. Many cities already have anaerobic digesters that convert sewage sludge at water resource recovery facilities (WRRFs) to biogas. Because of its abundance in landfilled waste (22%), food waste is of current critical concern to the US Environmental Protection Agency. Yard (flora) waste comprises an additional 7.8% of waste going to landfills. Both food and yard waste could be used to boost biogas production in WRRF digesters. One main question is: What WRRF locations with existing digesters are the best candidates to produce vehicle fuel from food/yard waste? In this paper, we present an optimization that balances trade-offs between food/yard waste transportation costs and capital/operating costs for expanding digesters. An example study is conducted for the City of Dallas, Texas.