7.1.4. Swine Wastewater

Employing a single-chamber MEC with a graphite-fiber brush anode, hydrogen gas was produced at a rate of 0.9–1.0 m<sup>3</sup> H2·m<sup>−</sup>2·day−<sup>1</sup> utilizing either pure or diluted swine wastewater (which may contain complex molecules that degrade at a slower rate than hydrogen). As a result, a greater allocation of carbon should be assured in order to meet the carbon demand that cannot be fulfilled by the organisms themselves. Undiluted swine waste matter would require a carbon-to-nitrogen ratio greater than 1.7 in order to degrade completely). COD removals ranged from 8–29% in 20 h tests and 69–75% in longer tests (184 h) that used full-strength effluent to achieve the highest levels of COD removal. The gas produced contained up to 77% ± 11% H2, with overall recoveries of up to 28% ± 6% of the COD contained within the waste matter being recovered as hydrogen [99].
