Swine diets: Impact of carbohydrate sources on manure characteristics and gas emissions

Swine manure management by hydrothermal carbonization: Comparative study of batch and continuous operation

Hydrothermal carbonization (HTC) is considered a promising technology for biomass waste management without pre-drying. This study explores the potential for swine manure management by comparing batch and continuous processes, emphasizing the benefits of the continuous mode, particularly for its potential full-scale application. The continuous process at low temperature (180 °C) resulted in a hydrochar with a lower degree of carbonization compared to the batch process, but similar characteristics were found in both hydrochars at higher operating temperatures (230-250 °C), such as C content (∼ 52 wt%), fixed carbon (∼ 24 wt%) and higher calorific value (21 MJ kg-1). Thermogravimetric and combustion analyses showed that hydrochars exhibited characteristics suitable as solid biofuels for industrial use. The process water showed a high content of organic matter as soluble chemical oxygen demand (7-22 g L-1) and total organic carbon (4-10 g L-1), although a high amount of refractory species such as N- and O-containing long aromatic compounds were detected in the process water from the batch process, while the process water from the continuous process presented more easily biodegradable compounds such as acids and alcohols, among others. The longer time required to reach operating temperature in the case of the batch system (longer heating time to reach operating temperature) resulted in lower H/C and O/C ratios compared to hydrochar from the continuous process. This indicates that the dehydration and decarboxylation reactions of the feedstock play a more important role in the batch process. This study shows the efficiency of the continuous process to obtain carbonaceous materials suitable for use as biofuel, providing a solution for swine manure management.

Impact of diet on hydrogen sulfide production: implications for gut health

PURPOSE OF REVIEW

Excessive hydrogen sulfide (H 2 S) production by the gut microbiota may contribute to the pathogenesis of multiple intestinal diseases, including colon cancer and ulcerative colitis. Therefore, understanding of dietary drivers of H 2 S production has potential implications for nutritional strategies to optimize gut health and treat intestinal diseases.

RECENT FINDINGS

Recent studies support a positive relationship between dietary protein intake and H 2 S production. However, protein rarely exists in isolation in the diet, and dietary fiber intake could reduce H 2 S production in humans and animals, even with ∼30% of calories derived from protein.

SUMMARY

These findings suggest that increased fiber intake may reduce H 2 S production irrespective of protein intake, enabling the ability to meet the metabolic demands of the illness while supporting gut health. Here we discuss two recent ulcerative colitis diet studies that illustrate this point.

Environmental impacts of eco-nutrition swine feeding programs in spatially explicit geographic regions of the United States

This study was conducted to determine greenhouse gas (GHG) emissions, water consumption, land use, as well as nitrogen (N), phosphorus (P), and carbon (C) balance of five diet formulation strategies and feeding programs for growing-finishing pigs (25-130 kg body weight) in the three spatially explicit geographic regions where the majority of U.S. pork production occurs. Feeding programs evaluated consisted of 1) standard corn-soybean meal (CSBM) diets, 2) CSBM containing 15% corn distillers dried grains with solubles (DDGS), 3) CSBM with 8.6% thermally processed supermarket food waste (FW), 4) low crude protein CSBM diets supplemented with synthetic amino acids (SAA), and 5) CSBM with phytase enzyme (PHY) added at 600 FTU (phytase units)/kg of diet. An attributional Life Cycle Assessment approach using a highly specialized, spatially explicit Food System Supply-Chain Sustainability (FoodS3) model was used to quantify GHG emissions, water consumption, and land use of corn, soybean meal, and DDGS based on county level sourcing. The DDGS, FW, and SAA feeding programs had less estimated N and P intake and excretion than CSBM, and the PHY feeding program provided the greatest reduction in P excretion. The FW feeding program had the least overall GHG emissions (319.9 vs. 324.6 to 354.1 kg CO2 equiv./market hog), land use (331.5 vs. 346.5 to 385.2 m2/market hog), and water consumption (7.64 vs. 7.70 to 8.30 m3/market hog) among the alternatives. The DDGS feeding program had the greatest GHG emissions (354.1 kg CO2 equiv./market hog) among all programs but had less impacts on water consumption (7.70 m3) and land use (346.5 m2) per market hog than CSBM and PHY. The SAA feeding program provided a 6.5-7.4% reduction in land use impacts compared with CSBM and PHY, respectively. Regardless of feeding program, the Midwest had the least contributions to GHG emissions and land use attributed to feed and manure among regions. Water consumption per market hog associated with feeding programs was much greater in the Southwest (59.66-63.58 m3) than in the Midwest (4.45-4.88 m3) and Mid-Atlantic (1.85-2.14 m3) regions. Results show that diet composition and U.S. geographic region significantly affect GHG emissions, water consumption, and land use of pork production systems, and the potential use of thermally processed supermarket food waste at relatively low diet inclusion rates (<10%) can reduce environmental impacts compared with other common feeding strategies.