Feasibility of incorporating all products of human waste processing into material cycling in the BTLSS

Possible risks for the functioning of cyclic processes in the experimental model of a closed ecosystem

The purpose of the present study is to consider a number of possible risks that may emerge when processed human wastes are involved into mass exchange processes as fertilizers for plants cultivated in the experimental model of the closed ecosystem (CEEM). The problems relating to the disruption of cycling processes in closed ecosystems can be tentatively divided into two groups: the problems that can be rather easily overcome and the chronic problems. Addition of plant inedible biomass to the soil-like substrate (SLS) can result in a decrease in plant productivity because of allelopathic interactions and enhanced growth of microorganisms. The 30% decrease in wheat productivity by the end of long-duration experiments in the CEEM, with plants grown on quasi-non-renewed solutions based on liquid products prepared by physicochemical mineralization of human wastes, was caused by lower resistance of the plants affected by toxicants accumulated in the solution because of incomplete mineralization of the wastes. The reason for the differences between the macronutrient inflows and outflows was that the donor of human wastes followed a European-type diet while the system produced only part of the plant-based diet. Moreover, macronutrients were partly sorbed in rooting substrates and became unavailable to plants: the substrates in the system retained about 50% of the Ca and 20% ÷ 25% of the Mg, Na, and P inflows over one cycle. These problems are temporary and can be minimized in the foreseeable future.

Factors affecting flavor perception in space: Does the spacecraft environment influence food intake by astronauts?

The intention to send a crewed mission to Mars involves a huge amount of planning to ensure a safe and successful mission. Providing adequate amounts of food for the crew is a major task, but 20 years of feeding astronauts on the International Space Station (ISS) have resulted in a good knowledge base. A crucial observation from the ISS is that astronauts typically consume only 80% of their daily calorie requirements when in space. This is despite daily exercise regimes that keep energy usage at very similar levels to those found on Earth. This calorie deficit seems to have little effect on astronauts who spend up to 12 months on the ISS, but given that a mission to Mars would take 30 to 36 months to complete, there is concern that a calorie deficit over this period may lead to adverse effects in crew members. The key question is why astronauts undereat when they have a supply of food designed to fully deliver their nutritional needs. This review focuses on evidence from astronauts that foods taste different in space, compared to on Earth. The underlying hypothesis is that conditions in space may change the perceived flavor of the food, and this flavor change may, in turn, lead to underconsumption by astronauts. The key areas investigated in this review for their potential impact on food intake are the effects of food shelf life, physiological changes, noise, air and water quality on the perception of food flavor, as well as the link between food flavor and food intake.