Protecting the environment through insect farming as a means to produce protein for use as livestock, poultry, and aquaculture feed

Securing protein for the approximate 10 billion humans expected to inhabit our planet by 2050 is a major priority for the global community. Evidence has accrued over the past 30 years that strongly supports and justifies the sustainable use of insects as a means to produce protein products as feed for pets, livestock, poultry, and aquacultured species. Researchers and entrepreneurs affiliated with universities and industries, respectively, from 18 nations distributed across North and South America, Europe, Asia, Africa and Australia contributed to the development of this article, which is an indication of the global interest on this topic. A brief overview of insects as feed for the aquaculture industry along with a review of the black soldier fly, Hermetia illucens (Diptera: Stratiomyidae), as a model for such systems is provided

Effect of high influent sulfate on anaerobic wastewater treatment

A laboratory-scale study was conducted using a completely mixed reactor with a constant influent-total-organic carbon (TOC) of 3750 mg/L to evaluate the effect of increasing influent-sulfate levels on anaerobic-treatment performance. The sulfate levels were increased stepwise from 333 to 666, 1000, 1333 and 1666 mg S/L. The results showed that an elevation of influent sulfate actually increased the TOC removal efficiency as long as the produced sulfide level did not induce toxicity. At 1333 mg S/L influent sulfate, the produced dissolved sulfide was 613 mg S/L (free sulfide = 228 mg S/L), which started to impose toxicity to the methane-producing bacteria (MPB). It was also found that the percent electron flow to the sulfate-reducing pathway increased with the increasing influent sulfate, but the direction toward the methanogenesis was correspondingly reduced. Nevertheless, under the experimental conditions tested, the majority of the influent organics was still degraded through the methanogenic pathway. Through this study, an oxidation-reduction-potential (ORP)-based oxygenation process was developed for online oxidation of sulfide in recirculating biogas. With controlled oxygen injection to raise the reactor's ORP by 25 mV, the residual sulfide in the reactor was almost totally eliminated. In case of over oxygenation, any excess oxygen was quickly consumed by the facultative organisms in the reactor, thereby imposing no toxicity to the MPB

Treatment of high sulfate and high strength wastewater in a single stage anaerobic reactor

In this study, a preset oxidation-reduction potential (ORP) was employed to regulate oxygen dosing for online sulfide toxicity control during anaerobic treatment of high sulfate wastewater. The experiment was conducted in an upflow anaerobic reactor (UAF), which was operated at a constant influent total organic carbon (TOC) of 6740 mg/L (equivalent to a chemical oxygen demand (COD) of 18000 mg/L) but with different influent sulfates of 1000, 3000 and 6000 mg/L. The reactor was initially run without oxygen injection at a natural ORP of about-290 to -300 mV and then was followed by oxygenation to raise ORP by +25 mV above the natural level for each influent sulfate level. With 1000 and 3000 mg/L influent sulfates, the produced sulfide levels did not impose any appreciable toxicity to methanogens even without oxygen injection. However, with 6000 mg/L influent sulfate without oxygen injections, the dissolved sulfide level quickly went up to over 800 mg/L which imposed a significant suppression on methanogenesis. Upon oxygen injection to raise the ORP by +25 mV, the dissolved sulfide was quickly reduced to 160 mg/L. If more oxygen was injected to raise the ORP by +50 mV, then dissolved sulfide further decreased to 12.2 mg/L with a concomitant improvement in methane yield by 45.9%. With a +25 mV preset ORP increase, it was found that at the 1000 mg/L influent sulfate the supplied oxygen was more than that needed for sulfide oxidation. The excess oxygen could be utilized readily by facultative heterotrophs for organic oxidation, which contributed 13.5% of the total COD removal in the UAF. At the higher sulfate levels of 3000 and 6000 mg/L, the facultative contributions to the total COD removal were only 4.7 and 4.1%, respectively. This study has clearly demonstrated that ORP is a workable and reliable means for regulating oxygen injection to achieve online sulfide toxicity control in a single-stage anaerobic system treating high sulfate wastewater