The University of Delaware’s (UD) Hong Li is part of a research team looking at how adding alum (aluminum sulphate) as an amendment to poultry litter reduces ammonia and greenhouse gas concentrations and emissions—specifically carbon dioxide—in poultry houses.

By Jaime Abella Sison

Li partnered with researchers at the United States Department of Agriculture (USDA), the University of Tennessee, and Oklahoma State University for the project. The results were recently published in the Journal of Environmental Quality.

Li, an assistant professor at the Department of Animal and Food Sciences (ANFS) in UD’s College of Agriculture and Natural Resources, said that the project is ongoing and that the main challenge for the poultry industry is controlling nutrient emissions from poultry houses and conserving energy while also providing for the welfare of the birds inside the houses.

Acid-based chemical compounds, alum, and PLT (poultry litter treatment)—another amendment—that are added to the bedding material in poultry houses prior to the birds entering have proven to be a very effective tool in controlling ammonia emissions. “In the poultry industry, ammonia is a major concern. Ammonia during the growth period is high, especially during the wintertime. Ammonia can do a lot of damage to the animal, especially the respiratory system, and can effect overall animal health and welfare,” said Li.

Also, if ammonia is emitted to the air from the poultry house, it is a precursor of fine particles and there are national Clean Air Act regulations from the Environmental Protection Agency that have strict guidelines for controlling emissions.

“We need to control the ammonia, not only for the animal health but also for the public health. That’s why I’m doing the research, to reduce the ammonia emissions and improve the animal health and the public air quality, especially for the rural areas, to make sure our agriculture is sustainable,” said Li.

Li said that there are several products on the market to control ammonia in poultry houses and alum is the preferred product for growers in Arkansas, where the study was conducted.

While adding alum to poultry litter is known to reduce ammonia concentration in poultry houses, its effects on greenhouse gas emissions had been unknown.

Li’s role in the study was on the engineering side and he helped Philip Moore, one of the authors of the paper and a pioneer researcher on alum in poultry production with the USDA, develop an automatic air sampling system to evaluate the emissions reduction by using alum in the broiler house.

“We not only looked at ammonia reduction, we also looked at the whole environmental footprint—how the alum could potentially impact the greenhouse emissions—and the results showed that we reduced quite a bit of carbon dioxide emissions,” said Li.

Carbon Dioxide Reduction

The carbon dioxide was reduced in two ways. First, because alum is an acidic product, it reduces microbial activity in the litter and reduces the ammonia emissions. Ammonia comes from uric acid being broken down by bacteria and enzymes. Once the uric acid is broken down, two products are created – one is ammonia and one is carbon dioxide.

“By reducing the bacterial activity, we reduce ammonia and also, we reduce the carbon dioxide; that’s one aspect of how we reduce carbon dioxide,” said Li.

Second, by using acid-based litter amendments in poultry litter, growers can reduce the ventilation rate and reduce fuel used for heating the poultry houses, especially during the
winter. “In the broiler industry, we want to control ammonia to improve animal health and
welfare. They have to keep the bird comfortable with optimum temperatures. However, if you want to have lower ammonia, you have to bring in more fresh air, remove more of the ammonia-laden air. As a result, you have to over ventilate the house,” Li said.

“That means you have to burn more fuel to keep the house warm. By using the acid-based
litter amendments, we can reduce the ventilation rate and the fuel use, which reduces the
carbon dioxide emission from the house through the heating process. Basically, if we reduce
the microbial activity and also reduce the heating, we can generate lower carbon dioxide

What’s the difference between Global Warming and Climate Change?

“Global warming” refers to the long-term warming of the planet. Global temperature shows a well documented rise since the early 20th century and most notably since the late 1970s. Worldwide, since 1880, the average surface temperature has gone up by about 0.8OC (1.4OF), relative to the mid-20th-century baseline (of 1951-1980). “Climate change” encompasses global warming, but refers to the broader range of changes that are happening to our planet. These include rising sea levels, shrinking mountain glaciers, accelerating ice melt in Greenland, Antarctica, and the Arctic, and shifts in flower/plant blooming times. These are all consequences of the warming, which is caused mainly by people burning fossil fuels and putting out heat-trapping gases into the air. The terms “global warming” and “climate change” are sometimes used interchangeably, but strictly they refer to slightly different things (

THOUGHT FOR THE MONTH: To accomplish great things, we must not only act but also dream, not only plan but also believe. – Anatole France

This appeared in Agriculture Monthly’s March 2016 issue.