5.7 Meat Production Methods

Because of the 10% rule, only about one-tenth of the energy in the feed an animal eats ends up stored in its body. So growing grain to feed livestock and then eating the meat takes far more cropland, water and energy than eating the grain directly. Commonly cited global estimates put the water needed for 1 kg of beef at about 15,400 liters, compared with about 4,300 liters for chicken and about 1,800 liters for wheat.

Livestock, especially cattle, sheep and goats, also produce methane as they digest grass. Methane is a strong greenhouse gas, roughly 25 to 30 times as effective as CO₂ at trapping heat over 100 years. Livestock farming also adds nutrient pollution from manure.

A concentrated animal feeding operation (CAFO) packs large numbers of animals, like cattle, pigs or chickens, into a small area. Feedlots are CAFOs for cattle. Animals are fed grain and soy to make them grow quickly, rather than grazing.

Advantages: CAFOs produce a lot of meat quickly and cheaply, which keeps prices low, and they use little land for the animals themselves.

• Manure: huge amounts pile up in one place, often stored in lagoons. Leaks, overflows and runoff send nitrogen, phosphorus and pathogens like E. coli into streams and groundwater, causing eutrophication and health risks.
• Air pollution: manure releases ammonia, methane and hydrogen sulfide, which create odor and health problems for nearby communities.
• Antibiotics: animals in crowded conditions are often given antibiotics routinely to prevent disease and sometimes to speed growth. Frequent use selects for bacteria that are resistant to antibiotics, which can spread to people and make human infections harder to treat.
• Feed: growing the grain requires cropland, fertilizer, pesticides, irrigation and fossil fuels.

In free-range grazing, animals graze on open pasture or rangeland for much of their lives. Their manure is spread out and fertilizes the soil. But if too many animals are kept on a pasture, manure can still run off and the soil can erode. Free-range systems need much more land, so the meat costs more, and free-range doesn't automatically mean antibiotic-free.

Rotational grazing divides pasture into sections and moves the herd from one section to the next. Each section gets time to regrow before animals return. This keeps plant cover, prevents overgrazing and spreads manure evenly.

Overgrazing happens when too many animals graze an area for too long, so plants are eaten faster than they can regrow. Bare soil is exposed to wind and rain and erodes. Hooves compact the soil, so less water soaks in and more runs off. Less hardy plants die and are replaced by weeds or nothing at all. Overgrazing also lowers biodiversity and reduces the carbon stored in plants and soil.

In dry regions, overgrazing combined with drought can lead to desertification: once-productive land loses its plant cover and fertile soil and becomes desert-like. Lands bordering deserts, like the Sahel south of the Sahara, are especially at risk. Rotational grazing and limiting herd sizes help prevent it, and restoring plant cover and conserving soil can slow or even reverse it.

Impacts differ a lot by animal. Ruminants like cattle and sheep give off the most methane and need the most land and water per gram of protein; chicken and pork need less, and plant protein much less.

Eating less meat, especially beef and lamb, lowers emissions of CO₂, methane and nitrous oxide (N₂O), saves fresh water and cuts the use of antibiotics and growth hormones. Better-quality feed and precision farming tools can also shrink livestock's impact. How big the benefit is depends on how the meat was produced and how land no longer used for livestock is managed.