From nitrogen-rich runoff to greenhouse gases and imported feed, the poultry industry’s footprint is much larger than most consumers see — and solving the manure problem is becoming urgent
-
By Steven Crook / Contributing reporter
Taiwanese sure do like their eggs, and they’re quite partial to chicken meat.
Per capita intake of chickens’ eggs has crept up to around 380 per year, and shortages in the first half of 2023 dominated the news cycle. Many of the processed egg products used by bakeries and fast-food chains, such as dried egg white, yolk powder and albumin derivatives, are imported. When it comes to the fresh shell eggs sold in supermarkets, Taiwan is in most years self-sufficient — but at least three-quarters of the country’s egg-laying hens are still raised in open-sided coops, leaving them exposed to bird flu and extreme weather.
The average Taiwanese ate 43.13kg of chicken meat in 2024, much of it in the form of chicken cutlets and popcorn chicken; per-person consumption here is twice that in Japan, South Korea or China. Domestic white broilers and local non-broiler varieties known as native chicken (土雞), silkie (烏骨雞, “black-boned chicken”) and free-range chicken (放山雞) account for 55 to 60 percent of the chicken meat sold. Strong demand for free-range chickens (which have lower fat content than indoor-housed broilers, but more protein, zinc and iron) is one reason why many traditional poultry farms continue to prosper.
Photo courtesy of Taiwan Livestock Research Institute
Among standard terrestrial livestock, chicken meat is almost always the greenest option. Like other livestock operations, however, both layer (egg) and broiler (meat) businesses have significant negative impacts. As anyone who’s stood downwind of such a place knows, even well-managed modern poultry houses vent strong odors, loose feathers, and airborne dander.
WATERSHED RISKS
An October 2010 study published in Agriculture, Ecosystems & Environment highlights the environmental risks of free-range chicken farms in Tainan City’s Longci District (龍崎). Because free-range birds deposit feces directly onto the ground, contaminants within their manure — which is rich in organic nitrogen and various forms of phosphorus — run off into local water systems. Consequently, researchers warned that these operations “are becoming a severe threat to southern Taiwan’s watersheds” and reservoir water quality.
Photo: Steven Crook
Feed production and processing is generally the single largest contributor to the carbon footprint of non-ruminant livestock operations. This is especially true in Taiwan, where almost all of the soy and feed-grade corn is shipped in from the US, Brazil or Argentina. The mountains of waste generated by major poultry farms must also be handled properly to prevent severe environmental fallout. Left untreated, manure releases nitrous oxide and methane, both of which are potent greenhouse gases. This organic waste also contributes to air pollution, eutrophication and soil acidification.
What goes into an animal influences what comes out of it, and local scientists believe that, by tinkering with feed mixes, it’s possible to ameliorate the harm done when raw manure is incinerated or converted to fertilizer. On Sept. 16 last year, researchers at the Ministry of Agriculture’s Taiwan Livestock Research Institute (農業部畜產試驗所) announced that replacing up to 4 percent of the protein in poultry feed with essential amino acids meaningfully reduces nitrogen and ammonia emissions from birds’ droppings, and thus the amount of nitrous oxide going into the atmosphere.
This improvement, they said, doesn’t affect egg quality or the growth of broilers. It also cuts feed costs. Poultry specialists overseas have noted that low-protein diets bring additional benefits to birds, including better gut health and greater resilience during periods of heat stress. The real test now is how quickly feed manufacturers will adapt their formulas to capitalize on this discovery.
Photo: TT file photo
MANURE SOLUTIONS
Gasification involves heating waste in a low-oxygen environment until its component hydrocarbons turn into synthesis gas (syngas). Because it’s drier, poultry litter is much better for this process than cattle or swine manure. Syngas can be burned to generate heat and/or electricity, or converted into liquid synthetic fuel.
A by-product of gasification is biochar, a charcoal-like substance that has multiple uses including enhancing soil health, regulating humidity in closed environments and immobilizing toxic metals so plants don’t absorb them and rain doesn’t wash them into nearby rivers.
Photo: CNA
Direct combustion turns a large quantity of predried manure into a much smaller volume of ash which can then be used as a slow-release phosphorus-potassium fertilizer. The heat completely sterilizes the material, eliminating viruses and pathogens like Salmonella and E. coli. However, it also destroys almost all of the nitrogen, the element that fuels plant growth and which crops require in large quantities. During the burning, the manure’s organic nitrogen is converted into nitrogen gas and nitrogen oxide, which escape into the atmosphere.
Composting manure is inexpensive, and the end product can be used as dry fertilizer. However, incompletely decomposed compost may contain pathogens, insect eggs and weed seeds. There’s another problem: composting one metric ton of poultry waste produces at least 2kg of methane, and as much as 8kg if it isn’t frequently “turned” or otherwise aerated to minimize anaerobic decomposition. Over a 20-year timescale, methane has a global warming potential 80 to 86 times that of carbon dioxide; keeping it out of the atmosphere should therefore be a priority.
A recent study published in March by Taiwanese scholars in Poultry Science quantified the carbon footprint of organic fertilizer derived from poultry manure via conventional composting with a near-identical commodity produced through high-temperature microorganism decomposition (HMD).
Photo: Chen Yen-ting, Taipei Times
Noting that HMD takes a mere seven days, compared to around 40 days for regular composting, they found that the life-cycle carbon footprint of HMD fertilizer, at 801kg of CO2e per metric ton, was 17 percent greater than that of fertilizer made by conventional composting.
This isn’t surprising, as HMD requires a fair amount of electricity to keep the temperature high enough. Yet it shouldn’t disqualify the technology; by comparison, the synthetic nitrogen fertilizers that underpin global food production carry a far heavier footprint of roughly 2.6 metric tons of CO2e. More worrying are the other environmental consequences noticed by the scientists. HMD fertilizer resulted in more than triple the freshwater ecotoxicity of standard compost, while its acidification impact was eight times greater.
Rather than convert chicken waste into fuel, biochar or fertilizer, a handful of farms have begun deploying black soldier fly larvae to tackle their manure challenges. These larvae, which grow up to 25mm in length, rapidly digest fresh waste. Harvested just before the pupal stage, they are dried, defatted and milled into a nutrient-rich insect meal. Recently approved by the Ministry of Agriculture for poultry and aquaculture feed, this powder offers a sustainable alternative to traditional soybean and fishmeal, while the extracted oils serve as valuable feed additives or biodiesel feedstock.
Part Two of this article will explore another approach to the manure problem: using it to produce combustible biogas.
Steven Crook, the author or co-author of four books about Taiwan, has been following environmental issues since he arrived in the country in 1991. He drives a hybrid and carries his own chopsticks. The views expressed here are his own.
