Animal manure - a huge and growing problem.
Printable PDF format 0.38MB [Download]The volume of livestock manure is mind-bogglingly huge. In many parts of the world, the problems caused by human waste is very substantial, causing significant environmental degradation. Add to this an even greater amount from animals raised for food. On a weight basis, the mass of cattle exceeds that of the whole human race.
consequence the volume of manure produced by these animals also
exceeds that produced by the human race. While many of these cattle are
widely distributed over range lands, a growing and significant
proportion of them are kept in intensive feedlots. Add to this 19
billion chickens and pigs, the majority of which are kept in
intensive production facilities, the amount of manure is gargantuan
and concentrated in relatively small areas of land. It has to
go somewhere: some is dried and used for fuel, much is spread on
farming land as fertilizer and some escapes directly into water run
off. Which ever way it goes within two years or so, it ends up by
adding huge amounts of nutrients to rivers which along with the run
off of fertilizer residues causes major problems with eutrophication
The estimated volume of animal waste is in the order of 13 billion tonnes per annum. In intensively raised livestock, dairy cows retain only about 20% of nitrogen (N) and 25% of phosphorus (P), pigs about 35% N and 33% P, and broilers 45% N and 20% P from their feed (Steinfeld 06). The rest ends up in the environment. A substantial amount of the nitrogen comes from chemical fertilizers and the phosphorous from mineral sources and is added to rather than recycled from the world's ecosystems. On a world scale nitrogen losses from manured agricultural lands into fresh water amounts to more than 12 million tonnes. Phosphorus leaching is in the order of 1.5 million tonnes (Steinfeld 06).
The effect of eutrophication on a massive industrial scale is frightening.
Water contamination by nitrates and phosphates from intensive animal production is now a world wide problem. It is most noticeable in the US where intensive animal production has been going on the longest but this is also a world wide problem. Chesapeake Bay on the eastern coast of the US is a prime example. The catchment area contains large numbers of piggeries and other intensive animal units, with animals outnumbering humans 11 to 1, amounting to 185 million in 2004! Eutrophication in the bay caused a rapid expansion of algae blooms and subsequent bacterial overgrown which consumes the oxygen creating extensive dead zones with serious reduction in marine creatures (Chesapeake Bay 04). There was also an explosion of the dinoflagellate Pfiesteria which is toxic to fish as well as humans, resulting in further reduction of fish numbers.
After very significant local activism and the application of federal and local laws, nutrient levels fell from their peak to 2004 by 15%, but they have a long way to go. To reach the goal of the Clean Water Act, a further reduction of 39 and 33% in nitrogen and phosphorous run off respectively would be required. Of even greater concern are the growing dead zones in off-shore areas.
Marine dead zones are a growing world wide
problem. A huge dead zone has
been created in the Gulf of Mexico from excessive nutrient from the
Mississippi River. Such nutrients cause a rapid growth of
micro-organisms and algae. When they die they sink to the bottom to
be consumed by bacteria which in turn use up most of the dissolved oxygen,
with levels dropping below
that needed to support the vast majority of living organisms.
The number of dead zones has been increasing rapidly each year and
is now estimated by Robert Diaz at the Virginia Institute of Marine
Science at more than 200 as shown in the following world map (Schrope
Industrial livestock production in China, Thailand and Vietnam has polluted the extensive shallow water areas of the South China Sea, causing red tides of toxic algae (Naylor 05). Europe has not escaped. The problem in the Netherlands is huge with nitrate levels in groundwater double allowable levels, prompting a major government initiative especially the reduction of pig numbers.
The oceans are being repopulated by primitive organisms driven by eutrophication. Our industrial society is overdosing the oceans with nutritients - nitrogen, phosphorous, carbon, iron, copper. These nutrients feed the excessive growth of harmful bacteria and algae. The situation is made worse by over fishing, removing many of the species that graze on algae. A good example of the problem is in Moreton Bay in Queensland where there has been an explosion of fire weed, Lyngbya majuscula, a highly toxic cyanobacteria. Contact with it causes severe burning making fishing almost impossible and swimming dangerous (Weiss 07). Urea from fertilizer use has caused an alarming rise in the neurotoxin producing diatom of the Pseudo-nitzschia group in Californian waters. High levels of this toxin have caused large numbers of deaths in marine mammals and birds since the toxin is concentrated in fish and shellfish. It is also very harmful to humans (Pearson 07). In many regions, jelly fish populations have exploded related to excess food and the decline in predator population.
Land degradation from animal waste is also a major problem. Much of the waste is spread on surrounding lands at rates vastly exceeding its capacity to use the nutrients, which has been assessed as high as 1000 kilograms of nitrogen per hectare (Gold 04). Also see section on water pollution.
(Chesapeake Bay 04) Chesapeake Bay Foundation Report. Keeping Manure Out of the Water. 2004
(Gold 04) Mark Gold. The global benefits of eating less meat. Compassion in World Farming Trust. 2004. Downloadable from www.eatlessmeat.org
(Naylor 05) Rosamond Naylor, Henning Steinfeld, Walter Falcon, James Galloway, Vaclav Smil, Eric Bradford, Jackie Alder, Harold Mooney. Losing the Links Between Livestock and Land. Science 2005;310:1621-1622.
(Pearson 07) Aria Pearson. Keeping tabs on toxic ocean threat. New Scientist 2007; 16June:18-19
(Schrope 06) Mark Schrope. The dead zones. New Scientist 2006; December 9: 38-42
(Steinfeld 06) Henning Steinfeld,
Pierre Gerber, Tom Wassenaar, Vincent Castel, Mauricio Rosales, Cess
de Haan. Livestock's long shadow: environmental issues and options.
LEAD/FAO publication 2006. Downloadable from