Making meat is an inefficient process, but it varies from animal to animal - beef is worse than chicken. Insects have been touted as extremely efficient compared with other animals with crickets cited near the top. It looks like there not as good as once thought and may require high quality food. But if you're into meat don't worry - black soldier flies may thrive on waste from other animals.
from an article in PLoS ONE
Crickets Are Not a Free Lunch: Protein Capture from Scalable Organic Side-Streams via High-Density Populations of Acheta domesticus
Mark E. Lundy1, Michael P. Parrella2
1 University of California Division of Agriculture and Natural Resources, Colusa, CA, United States of America,
2 Department of Entomology and Nematology, University of California Davis, Davis, CA, United States of America
It has been suggested that the ecological impact of crickets as a source of dietary protein is less than conventional forms of livestock due to their comparatively efficient feed conversion and ability to consume organic side-streams. This study measured the biomass output and feed conversion ratios of house crickets (Acheta domesticus) reared on diets that varied in quality, ranging from grain-based to highly cellulosic diets. The measurements were made at a much greater population scale and density than any previously reported in the scientific literature. The biomass accumulation was strongly influenced by the quality of the diet (p<0.001), with the nitrogen (N) content, the ratio of N to acid detergent fiber (ADF) con- tent, and the crude fat (CF) content (y=N/ADF+CF) explaining most of the variability be- tween feed treatments (p = 0.02; R2 = 0.96). In addition, for populations of crickets that were able to survive to a harvestable size, the feed conversion ratios measured were higher (less efficient) than those reported from studies conducted at smaller scales and lower population densities. Compared to the industrial-scale production of chickens, crickets fed a poultry feed diet showed little improvement in protein conversion efficiency, a key metric in determining the ecological footprint of grain-based livestock protein. Crickets fed the solid filtrate from food waste processed at an industrial scale via enzymatic digestion were able to reach a harvestable size and achieve feed and protein efficiencies similar to that of chickens. However, crickets fed minimally-processed, municipal-scale food waste and diets com- posed largely of straw experienced >99% mortality without reaching a harvestable size. Therefore, the potential for A. domesticus to sustainably supplement the global protein supply, beyond what is currently produced via grain-fed chickens, will depend on capturing regionally scalable organic side-streams of relatively high-quality that are not currently being used for livestock production.