Final Report: Biofuel Production from Grease Trap WasteEPA Contract Number: EPD16002
Title: Biofuel Production from Grease Trap Waste
Investigators: Wilson, Donald
Small Business: Environmental Fuel Research, LLC
EPA Contact: Richards, April
Project Period: February 1, 2016 through January 31, 2018
Project Amount: $300,000
RFA: Small Business Innovation Research (SBIR) - Phase II (2015) Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , SBIR - Waste to Energy Systems
Grease Trap Waste (GTW) is one of the few remaining sources of oil without value. Unlike yellow grease (used cooking oil), restaurants pay to have it hauled away and the haulers pay a tipping fee to have it incinerated, land-filled or prepared for land application. Environmental Fuel Research, LLC (EFR) has developed technology to convert GTW into biodiesel with a robust suite of techniques. The purpose of this Phase II SBIR was to evaluate commercial potential of technology for extracting oils from GTW and converting it to biodiesel by scaling up the process in a pilot-plant facility with a fifty gallon batch processor. The main research and development activities conducted during this project included: arranging access to a suitable site for construction of the pilot-scale process; design, construction, and operation of the pilot-scale process; laboratory evaluation of alternative technologies for key portions of the project; focused research on desulfurization by vacuum distillation and other techniques; and Techno-Economic Analysis (TEA) of a potential full-scale GTW-to-biodiesel process.
GTW is by its nature, a highly variable feed stock which is high in free fatty acids and typically contains approximately 300-500 ppm sulfur. Traditional biodiesel processing techniques favor feed stocks low in free fatty acids and Government regulations require sulfur content of on-road Diesel fuel to be under 15 ppm. Prior research has shown that robustly achieving sulfur content below 15 ppm is the key technical challenge to a successful GTW-tobiodiesel process; this conclusion was confirmed in this project as fuel testing showed the only specification which was not consistently met by using the process in this project was sulfur content.
During this project, a pilot plant was built and operated in the Grease Thickening building at the Delaware County Regional Water Quality Control Authority (DELCORA). DELCORA operates one of the region’s largest grease receiving processes, where tanker trucks from numerous regional haulers offload the GTW collected primarily from restaurant wastewater grease interceptors. After being offloaded at DELCORA, the grease is “thickened” or partially dewatered. For this project, EFR constructed a series of heated settling tanks which EP-D-16-002: SBIR Phase II Project: Biofuel Production from Grease Trap Waste Executive Summary – Final Report Environmental Fuel Research, LLC were designed to transfer, liquefy and filter the Fat, Oil, and Grease (FOG) from GTW. Filtered and dewatered FOG from GTW is called brown grease, which is then transferred to a batch processor which was designed as a bubble column reactor for converting brown grease into Fatty Acid Methyl Esters (FAME), the primary component of biodiesel. This patented reactor technology was developed by EFR partner Richard Cairncross, Ph.D., at the Chemical Engineering Department of Drexel University as a robust system for conversion of low-quality feed stocks at ambient pressure and low temperatures.
After conversion from brown grease to crude biodiesel the material is dark in color and low in viscosity. The crude FAME is purified by distillation in a column operating under vacuum; the resulting distillate is low in viscosity, light in color and very clear (Figure 2). An additional polishing step, using an adsorbent further purifies the FAME and reduces sulfur content. The resulting fuel was mixed into an industry standard blend of B20 and used to successfully fuel EFR’s 2001 Ford F250 with 7.3L turbo diesel. Techno-economic analysis was used to evaluate the potential economic performance of a full-scale GTW-to-biodiesel process based on results from laboratory and pilot-scale experiments.
A facility already receiving and thickening/dewatering GTW can upgrade it to brown grease via heating and settling. Using readily available tanks and plumbing, a bubble column reactor can convert brown grease into crude biodiesel. Such as system requires no exotic enzymes, proprietary chemistry or elaborate equipment. The conversion process operates reliably at ambient pressure and relatively low temperatures, using readily-available industrial chemicals. Purification of the reaction products is achieved using distillation and adsorption. Distillation and adsorbents are effective at reducing sulfur content but at present are slightly short of reliably achieving specification. Table 1 displays quality of several samples of biodiesel produced during this project measured at a commercial fuel testing laboratory. The results in Table 1 show that the only fuel quality metric not met by the fully-treated samples was the sulfur content. After purification, the resulting fuel typically contains approximately 25ppm – 50ppm sulfur, a reduction of 90% but still over the required specification. Subcontracts with Drexel University and the USDA Eastern Regional Research Center enabled a comprehensive study of numerous adsorbents, comparison of various distillation technologies as well as novel methods of desulfurization. Laboratory-scale desulfurization experiments using reactive desulfurization and enhanced adsorption strategies were effective at reducing sulfur content to 10-15 ppm and scale-up of these technologies will be evaluated in future work. Techno-economic analysis (TEA) shows that the economic profitability of the GTW-tobiodiesel process is sensitive to the capacity of the process and availability of GTW or inexpensive brown grease. The base case TEA scenario produced about 1 million gallons per year of biodiesel from GTW and had marginal economics with a simple payback time of over years. However doubling the processing capacity reduced the simple payback time to less than 4 years.
GTW is a low-value feedstock that can be converted into biodiesel using mature chemical processing technologies. A combination of distillation and adsorption can meet fuel specifications, but it is difficult to reliably achieve sulfur contents below 15 ppm. Further research on deep desulfurization is needed for a robust process that meets all fuel specifications. TEA shows that GTW-to-biodiesel processes can be economically viable, especially at process capacities above 2 million gallons of biodiesel per year; at this scale, a regional network of GTW management is necessary to provide a sufficient quantity of feedstock.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
|Other project views:||All 2 publications||1 publications in selected types||All 1 journal articles|
||‘Longitudinal Study of Wastewater Greases and Their Potential for the Production of Biofuels,’ Megan E. Hums, Hrial Amin, Ta-Chi Tsao, Mira S. Olson, Sabrina Spatari, and Richard A. Cairncross, Energy and Fuels, Article ASAP January 11, 2018, DOI:10.1021/acs.energyfuels.7b03550.||