Chicken Manure: Breaking Down The Chemistry

Chicken manure is a valuable source of nutrients and can be used as compost to fertilize plants and gardens. It is rich in organic matter and contains nutrients such as calcium, sulfur, magnesium, nitrogen, potassium, phosphorus, manganese, copper, zinc, and iron. Chicken manure can be broken down through composting, which can be done through cold or hot methods, to create compost that can be used in gardening. Chicken manure is also used in anaerobic digestion, a process that breaks down organic matter to produce biogas, a mixture of methane and carbon dioxide, that can be burned as fuel. Environmental engineers are working on developing methods to help farmers turn chicken manure into valuable products while also reducing nutrient pollution, specifically nitrogen and phosphorus, that can negatively impact nearby waterways.

Composting chicken manure

Chicken manure is a valuable source of nutrients and can be used to create nutrient-rich compost for plants and gardens. Composting chicken manure is a great way to manage chicken waste while investing in a healthy homestead.

There are two methods of composting: cold composting and hot composting. Cold composting requires minimal maintenance and can be done by simply starting a compost pile and allowing the materials to naturally decompose. This process is slower and can take 6-12 months to complete. Hot composting, on the other hand, requires more maintenance but converts chicken manure into compost faster. This method involves bringing the compost pile up to 104-160°F for an extended period of time through proper management of moisture and turning.

To start composting chicken manure, you will need a compost bin or pile. The bin should be at least 1 cubic yard in size (3x3x3 feet) and placed in an area with good drainage and some shade. It is ideal to have two bins, with one bin in the hot compost phase and the other in the curing phase.

The key to successful composting is maintaining the right balance of materials. A general rule of thumb is to use 25-30 parts carbon-based material to 1 part nitrogen-based material. Carbon-based materials include brown, dry materials such as sawdust, wood chips, straw, dry leaves, newspaper, cardboard, and peanut shells. Nitrogen-based materials include green, wet materials such as vegetable scraps, chicken waste, coffee grounds, garden and grass clippings, and weeds. Chicken manure can make up one-third of the material but should be balanced with carbon-based materials.

Moisture is also important for composting. The compost materials should be about 50-60% moisture, damp but not dripping. This can be achieved through rain or intentional watering, which helps get nutrients to the microorganisms during the composting process.

Additionally, proper airflow is necessary for the microorganisms responsible for composting to survive. Turn or mix the compost pile at least once a week to add oxygen and promote decomposition.

Hot composting requires reaching and maintaining a temperature of 130-160°F for 3 days to destroy pathogens. A compost temperature gauge can be purchased to help monitor the temperature.

Once the composting process is complete, the compost should have a loamy smell and should not smell like faeces. The compost can then be used in gardens or for potted plants, providing a rich source of nutrients for the soil.

Anaerobic digestion

Chicken manure is an agricultural waste material with a high biomass potential. It is a typical feedstock for anaerobic digestion due to its high nitrogen content. However, the high nitrogen content can also cause problems, leading to ammonia inhibition which negatively impacts the stability of AD systems and can even cause system failure. Dilution is necessary to decrease the ammonia inhibition effect, but this leads to a large amount of effluent being produced, which is difficult to use.

Dry anaerobic digestion has some advantages over wet digestion, including reduced reactor volume, higher volumetric methane yield, lower energy consumption, less wastewater production, and lower logistic costs for fertilizers. However, studies have shown that the process is unstable. Co-fermentation, ammonium/ammonia removal, and adaptation of the microbial consortium have been used to decrease the effect of ammonia inhibition. A non-volatile sorbent located in the reactor can also decrease ammonia content during wet anaerobic digestion.

The dry batch anaerobic digestion process is a waste treatment technology most appropriate for the treatment of stackable (non-free-flowing), fibrous and contaminant-containing dry feedstock materials. Porous materials, such as straw and woodchips, can be used as substrate additives to enhance material mixture properties and allow sufficient percolation.

Extracting phosphorus

Chicken manure is a valuable source of phosphorus, an agriculturally vital nutrient. Phosphorus extraction methods are important for farmers who need phosphorus for their crops and for those who can no longer apply it to their fields due to high soil levels.

One phosphorus extraction method involves using reactors to treat a slurry of poultry litter. In the first reactor, the slurry's pH is lowered to about 5, releasing ammonium and phosphates into the water. The liquid is then separated from the solid matter and pumped into a second reactor, where the pH is increased to about 9, causing phosphorus-rich minerals to precipitate out. In lab-scale tests, engineers have recovered between 80 and 90% of the phosphorus in a litter sample using this method.

Another phosphorus extraction method involves incinerating chicken manure to produce ash, which can then be treated with hydrochloric acid to obtain a phosphorus-rich solution. By gradually changing the pH of this solution to 3, 4, and 8, phosphorus can be recovered as a precipitate. At pH 4, for example, 84% of the phosphorus in the original solution can be recovered as CaHPO4 · 2H2O with a purity of 92%.

Other methods of phosphorus extraction from chicken manure include using anaerobic digestion to produce biogas, and gasifying the manure into syngas, a fuel composed primarily of hydrogen and carbon monoxide. These technologies can help increase the sustainability of chicken farming by providing valuable products while also reducing nutrient pollution that can harm nearby waterways.

Chicken manure is also a good source of phosphorus for the production of universal agricultural fertilizer. Struvite, for example, can be produced by acidifying poultry manure ash extract, supplementing it with magnesium, and adjusting the pH to about 8.5. This process yields a multi-nutrient fertilizer with high levels of macroelements such as phosphorus, potassium, and magnesium.

Effects on plants

Chicken manure is a valuable source of nutrients and can be used as a natural fertilizer for plants. It contains nutrients such as calcium, sulfur, magnesium, nitrogen, potassium, phosphorus, manganese, copper, zinc, and iron. These nutrients are essential for plant growth and can be released into the soil through composting.

Composting chicken manure involves breaking it down into its chemical compounds so that it can be easily absorbed by plants. There are two main methods of composting: hot composting and cold composting. Hot composting is faster and is suitable for warm climates or sunny areas, requiring only 3 months for the manure to break down into compost. Cold composting, on the other hand, is a slower process and may take 6 to 12 months to complete.

Once the chicken manure has been aged and turned into compost, it can be applied to gardens or potted plants. It is recommended to mix the compost with gardening or potting soil and apply a 1-2 inch thick layer over the garden annually. Applying chicken manure compost improves soil productivity and enhances plant growth and crop quality.

Chicken manure has been found to increase soil organic matter, which benefits nitrogen-loving plants such as tomatoes, peppers, leafy greens, cucumbers, and sweet corn. It also increases the water content in plants, improving their uptake of nitrogen. This results in higher levels of soluble nitrogenous compounds, such as free amino acids, which are essential for cell function and plant health.

In addition to its effects on soil and plant health, chicken manure can also be used to create value-added products through various treatment processes. These processes include pyrolysis, gasification, anaerobic digestion, and hydrothermal liquefaction. For example, anaerobic digestion breaks down the organic matter in chicken manure to produce biogas, a mixture of methane and carbon dioxide that can be used as clean energy.

Odorous compounds

Chicken manure contains several odorous compounds, including ammonia, dimethylamine (DMA), trimethylamine (TMA), indole, phenol, and butyric acid. These compounds can have harmful health effects on humans and animals, as well as the chickens themselves. Long-term exposure to these compounds can cause irritation of mucosal membranes in the respiratory tract, tracheal irritation, air sac inflammation, conjunctivitis, dyspnoea, respiratory tract damage, reddening, corneal clouding, reduction in respiratory rate, and central nervous system disturbances.

Ammonia, DMA, TMA, and butyric acid have been found to increase DNA damage in a dose-dependent manner, with genotoxicity levels as high as 73.2 ± 1.9%. Phenol and indole, on the other hand, induced extensive DNA damage regardless of the concentration used. These compounds can also cause cytotoxicity, or cell destruction, which may lead to cancer-causing mutations.

The cytotoxicity of these odorous compounds was demonstrated using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and PrestoBlue assays in the chicken Leghorn Male Hepatoma (LMH) cell line. Similar effects were observed in the MTT and LDH assays, suggesting that while not all cytotoxic chemicals induce genotoxicity, genotoxic substances may still cause DNA damage at non-cytotoxic concentrations.

In summary, the odorous compounds found in chicken manure can have significant negative impacts on the health of humans, animals, and chickens, and proper management of this waste is essential to minimize potential harm.

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