| SUMMARY: Insects may be a more environmentally-sustainable source of protein than livestock. |
Lifestock is a major greenhouse gas contributor, nearly 20% of total anthropogenic emissions. They are also responsible for almost two-thirds of anthropogenic ammonia emissions which, in addition to being a pollutant in itself, can contribute to nitrous oxide emissions with the assistance of soil bacteria.
Given these facts, it makes sense to obtain protein from other sources besides conventional livestock; plants probably come to mind first as the most feasible source. Dennis Oonincx (Wageningen University, The Netherlands) and coworkers have investigated the environmental sustainability of raising edible insects, focusing on their production of carbon dioxide, methane, nitrous oxide, and ammonia.
Insect quantitations.
The scientists studied mealworms, house crickets, migratory locusts, sun beetles, and cockroaches. The latter two are not generally considered edible, but they are nevertheless a potential viable protein source, due to their consumption of a wide range of feed and the minimal time investment required to raise them in large numbers.
Between three and six trials were carried out with each insect species over the course of three days in separate respiration chambers. The day length, temperature, and humidity were set to values used by commercial companies (e.g. 12 hours of daylight, 28°C, and 70% humidity for the crickets), and each species was fed a specific diet (e.g. wheat bran and ryegrass for the sun beetles).
Environmental sustainability.
Since insects (unlike livestock) don't regulate their body temperature within a small temperature range, it stands to reason that a greater percentage of their food intake is spent on growth. Consequently, they are probably a more sustainable source of protein than livestock.
The insect methane, nitrous oxide, and carbon dioxide emissions (per kilogram of weight gain) were almost always well below that of pigs and cattle. For example, the carbon dioxide emissions of migratory locusts was 18 grams per kilogram weight gain, while that of pigs ranges from 80 to 1,130.
Nitrous oxide emissions appeared to highly variable. This may be due to experimental difficulties.
Nevertheless, greenhouse gas emissions from the insects were typically 1% of that from ruminants (e.g. cattle), and a greater percentage of the feed is converted to body mass. While the data of Oonincx and coworkers suggests that insects are a more environmentally-sustainable source of protein than livestock. a more complete study (i.e. everthing involved from initial production to final distribution and cleanup) is still needed.
NOTE: The scientists' research was funded by Wageningen University.
Oonincx, D. G. A. B., van Itterbeeck, J., Heetkamp, M. J. W., van den Brand, H., van Loon, J. A., & van Huis, A. (2010). An Exploration on Greenhouse Gas and Ammonia Production by Insect Species Suitable for Animal or Human Consumption PLoS ONE, 5 (12) DOI: 10.1371/journal.pone.0014445