The Costs of Photorespiration to Food Production Now and in the Future

Photorespiration is essential for C3 plants but operates at the massive expense of fixed carbon dioxide and energy. Photorespiration is initiated when the initial enzyme of photosynthesis, ribulose-1,5-bisphosphate carboxylase/ oxygenase (Rubisco), reacts with oxygen instead of carbon dioxide and produces a toxic compound that is then recycled by photorespiration. Photorespiration can be modeled at the canopy and regional scales to determine its cost under current and future atmospheres. A regional-scale model reveals that photorespiration currently decreases US soybean and wheat yields by 36% and 20%, respectively, and a 5% decrease in the losses due to photorespiration would be worth approximately $500 million annually in the United States. Furthermore, photorespiration will continue to impact yield under future climates despite increases in carbon dioxide, with models suggesting a 12–55% improvement in gross photosynthesis in the absence of photorespiration, even under climate change scenarios predicting the largest increases in atmospheric carbon dioxide concentration. Although photorespiration is tied to other important metabolic functions, the benefit of improving its efficiency appears to outweigh any potential secondary disadvantages.This article is from Annual Review of Plant Biology 67 (2016): 107, doi: 10.1146/annurev-arplant-043015-111709. Posted with permission.</p

Valorisation of human excreta for recovery of energy and high-value products : a mini-review

The current approach to managing waste is one of the major reasons for ecosystem imbalances. In many parts of the world, human excreta is indiscriminately dumped in the environment, leading to the entry of high concentrations of nutrients and pathogens. In urban sanitary systems, nutrients are often not recovered, but large amounts of natural resources (e.g. water) are used for treating wastes at the expense of the environment. These practices are unsuitable and pose risks to human health and the environment, as such current efforts are geared towards providing on-site sanitation and opportunities for nutrient and resource recovery. This mini-review summarises the efforts to valorise human waste and process routes for the recovery of value-added products. These involve a review of ecological sanitation, systems that safely collect and treat human waste in situ and advanced waste-to-energy systems to convert recovered materials to fuels, heat and/or electricity. Focus is given to low-cost technological solutions that offer ecological benefits and opportunities to recover useful products. The barriers and opportunities to the adoption of on-site sanitation and appropriate technologies are discussed, considering current limitations and potential benefits. There are opportunities to recover useful products from human wastes; however, further research is needed to ascertain the value and impact of recovered products