Chitin Lengthens Power Production in a Sedimentary Microbial Fuel Cell

Abstract

An emerging technology that could be utilized for ocean energy production is the microbial fuel cell. Microbial fuel cells are able to oxidize biodegradable fuels, such as organic waste, to generate electrical power. The sediment microbial fuel cell (SMFC) is a specialized subset of microbial fuel cells relevant in generating energy in the ocean environment. SMFCs are devices which are able to directly produce electrical energy by bacteria consuming biodegradable compounds in marine sediments. In sediments with low organic carbon, SMFCs have only been observed to provide relatively low amounts of power. Therefore, one hypothesis was to evaluate power production in a SMFC post an addition of an external carbon source. However, because this is in a seawater system, the carbon source should be in a solid phase. Types of solid amendments can include simple plant materials (lignin/cellulose) or animal by-products (chitin, deceased organisms, or other waste products). In this study, chitin from shrimp shell waste was used as a method of increasing organic carbon to increase or prolong power production and for SMFC operation in sandy, low carbon sediments. SMFC's were tested in two San Diego Bay sediment types; low total organic carbon (TOC) and average TOC: 0.2% TOC and 2.5% TOC, respectively. SMFC units with chitin wrapped in water soluble tape were evaluated under static sea water conditions, as well as in the field. Results for chitin from shrimp shell waste indicated that power density was greater by a factor of 2 relative to control units in sediments with 2.5% TOC; and in sediments with low TOC, 0.2%, power output is 100 times greater. Therefore, these data in both normal and low organic carbon sediments demonstrate that chitin enhances and lengthens power production.