Letters▼ Free hogs produce less gas The front cover of the July 15, 2005, issue of ES&T shows three hogs on pasture rooting in the ground. The image promotes the article entitled “Biofiltration for Mitigating Methane Emissions from Animal Husbandry” (Environ. Sci. Technol. 2005, 39, 5460–5468), which is mainly concerned with the use of biofilters to remove methane from “animal houses and manure storage” emissions. I believe that the research is needed for today’s agricultural production models. My complaint is with the picture. Most hogs in the U.S. are raised in confinement buildings where all manure is in liquid form and is stored in lagoons or in
© 2005 American Chemical Society
pits under the confinement building. This liquid manure emits many gases, including methane, carbon dioxide, ammonia, and hydrogen sulfide, mainly due to anaerobic decomposition. The picture, however, conveys an alternative production model, raising hogs on pasture. While this model is not very common, it is gaining in popularity because of better living conditions for the hogs and the flavor of the meat produced. This model is better for the environment in that much of the manure is quickly assimilated into the soil. This scenario involves the aerobic decomposition of the manure and is unlikely to lead to high emissions of methane, ammonia, or hydrogen sulfide. This
model also allows the farmer to recover more of the fertilizer value of the manure rather than losing much of it to nutrient pollution. I believe that the picture implies to the reader that all animal production models cause high emissions of undesirable gases, when in reality pasture-based models contribute much lower levels of emissions of this type. I encourage ES&T to publish A-page articles showing the environmental impacts of confinement- versus pasture-based production models. MATTHEW FASNACHT Farmer and Environmental Chemist Southeast Missouri State University
[email protected] OCTOBER 15, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY ■ 415A
