(http://www.newscientist.com)
IT'S extreme recycling. Why grow crops on manure when you could just take the good stuff directly from it? Even better, maggots could help.
Global food prices have soared in recent years, and animal feed is no exception. "Maggot cake" could provide a high-protein food source for farm animals that is not only readily available, but recaptures nutrients in manure and other waste far more efficiently than existing methods.
"The real story is that we are mining an unexploited resource, and what's the last great unmined resource? It's our own waste," says Howard Bell of the UK Food and Environment Research Agency in York. With demand for food growing, "anything that can address a looming protein crunch is a good thing", he says.
Bell and other researchers are investigating the potential of growing maggots on manure, food and brewery waste. Once they have grown fat, the maggots are harvested, dried and crushed into a protein-rich powder for feeding to chickens, fish, pigs and other farm animals.
European farmers currently import 80 per cent of their animal feed, mainly soy from South America. US farmers face a feed crisis too. For example, the price of maize fed to pigs in the US has trebled since 2007. That's because new regulations and subsidies introduced at the time made it more profitable for maize growers to sell their crop for biofuel, reducing the supply for farmers.
The idea of harnessing maggots to address this problem is gathering pace. Much research has already been done in the US, South Africa and Spain, and next year could see the first commercial plant, probably in South Africa. Meanwhile, a US company called OVRSol is in talks with a major international food company to fund a pilot plant, followed by a full-scale commercial facility.
So exactly how much protein can be extracted from waste using maggots? Bell has been feeding chicken manure to housefly maggots as part of a three-year project. He says that at the moment, a tonne of manure yields about 100 kilograms of larvae, from which he can produce between 12.5 and 35 kg of feed.
The product is as rich nutritionally as the soy and fishmeal currently used as animal feed, Bell says. He presented his preliminary results last week at aconference in Edinburgh, UK, adding that he is confident of raising yields further by adjusting factors like the air and water content of the manure.
Allan Finney of OVRSol says his firm intends to feed its black soldier-fly maggots on waste from the food industry at first, and then on manure. Tests by the company suggest that the larvae can reduce manure to half its original volume, and because they outcompete and consume bacteria such as E. coliand Salmonella, the manure doesn't putrefy and essentially gets sterilised and deodorised. It can then be used as compost.
AgriProtein based in Cape Town, South Africa, is close to raising the funds it needs for a full-scale factory next year. Rather than manure, it feeds housefly maggots on a mixture of abattoir blood and bran, says company founder Jason Drew. He thinks the factory could produce around 100 tonnes of maggot cake a day.
Because the protein content of maggot cake matches that of soy and fishmeal, it could fetch a similar price, Bell says. Today that's around £800 or £900 a tonne. The maggots are about 50 per cent protein and a quarter oil by weight, and Bell says the fat could easily be separated off for sale as fuel or a food additive, for example in salmon feed. The maggots also yield their structural material, chitin, which is used as a stabiliser in many pharmaceutical products and as a binder in adhesives.
The economic potential is huge, says Finney. He calculates that manure from the 280 million chickens reared every year in the US could be converted to protein, fat and chitin worth at least $660 million. The corresponding figure for pigs could be as high as $5 billion, he says.
But is meat from fish and animals fed on maggot cake likely to be safe to eat? Drew says nothing is happening that wouldn't take place harmlessly in nature. "We're all eating trout from streams, and guess what they eat?" he says. Likewise, chickens, pigs and other farm animals all eat grubs and maggots that they find while foraging. Maggot cake is just a more concentrated form.
Finney agrees. He points out that the human consumer of meat from animals fed the maggots is two stages away from the manure, digested first by the maggots and then by the animals. This contrasts with consumers of organic vegetables, who are only one stage away, as the manure directly feeds the crops.
But with the memory of BSE, commonly known as mad cow disease, still fresh in the UK, people may be wary of such recycled products. The spread of BSE was traced to the practice at the time of including bovine material in feed intended for cows, and it spread exponentially through cows eating infected brain tissue. Bell says that because of this, his project specifically excludes the use of any animal parts.
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