Greenhouse gas emissions when composting manure from cattle fed wheat dried distillers’ grains with solubles

Abstract

Dried distillers' grains with solubles (DDGS) are a co-product of ethanol production that is increasingly available for use as a livestock feed. Including DDGS in diets could affect animal manure properties and impact manure management strategies. The objectives of this study were to investigate changes in the rate of greenhouse gas (GHG) emissions during composting and final properties of manure compost when DDGS is included in feedlot cattle diets. Treatments were: (1) Control; manure from cattle fed a typical finishing diet containing barley (Hordeum vulgare L.) grain and silage and (2) DDGS; manure from cattle fed a finishing diet with 60% DDGS from wheat (Triticum aestivum L.) in the dietary ration. Manure, consisting of feces, urine and wood shavings, was composted in open windrows. Samples were collected for analysis at initiation and completion of composting. Greenhouse gas surface fluxes were collected weekly during the first 4 weeks and every 2-3 weeks for the remainder of the composting period. The DDGS compost had lower total C, but similar total N (TN) content relative to Control, reflecting the initial manure conditions. The DDGS compost also had higher moisture, higher water-extractable NH 4 ? and NO 3 -, a greater fraction of TN in available form, and a lower pH than the Control. The O 2 consumption and N 2 O emission from DDGS compost were higher, whereas CO 2 and CH 4 emissions were similar to Control. The higher N 2 O emissions from DDGS compost were likely related to the high water-extractable N content in DDGS manure. Increased use of DDGS in feedlot diets may have environmental repercussions that include greater emissions of GHG (N 2 O) during manure composting. From an end user perspective, enhanced availability of N could increase the nutrient value of the compost for crop production.

A Snapshot of Greenhouse Gas Emissions from a Cattle Feedlot

“…These are higher than the 2.6 g CH 4 -C m -2 d -1 and 0.1 g N 2 O-N m -2 d -1 found by Hao et al (2011) for composting feedlot manure over a 100-d period. Our rates would be reduced if we could calculate emissions per unit of manure surface area as Hao et al (2011) reported. A similar calculation for NH 3 gives emissions of 1.8 g NH 3 -N m -2 d -1 , N 2 O, and NH 3 from feedlot pens, manure stockpiles, and run-off pond and CH 4 yield, N loss, # Actual calculation was -0.1 g animal -1 d -1 .…”

“…Dividing manure emissions by the ground area covered by the manure piles (72,000 m 2 ) gives emissions of 3.9 g CH 4 –C m −2 d −1 and 0.37 g N 2 O–N m −2 d −1 . These are higher than the 2.6 g CH 4 –C m −2 d −1 and 0.1 g N 2 O–N m −2 d −1 found by Hao et al (2011) for composting feedlot manure over a 100‐d period. Our rates would be reduced if we could calculate emissions per unit of manure surface area as Hao et al (2011) reported.…”

“…These are higher than the 2.6 g CH 4 –C m −2 d −1 and 0.1 g N 2 O–N m −2 d −1 found by Hao et al (2011) for composting feedlot manure over a 100‐d period. Our rates would be reduced if we could calculate emissions per unit of manure surface area as Hao et al (2011) reported. A similar calculation for NH 3 gives emissions of 1.8 g NH 3 –N m −2 d −1 , much less than the 15 g NH 3 –N m −2 d −1 (per ground area) found by Sommer et al (2004) from feedlot manure over 7 d after removal.…”

A major pathway for carbon and nitrogen losses — Gas emissions during storage of solid pig manure in China

“…We found that CO 2 emission is strongest from day 30 onwards of storage, indicating that microbial activity was high during this period. The CO 2 -C losses accounted for 57.23% of the initial total C. This was consistent with the findings of other studies on static compost pile which reported losses of CO 2 -C between 46 and 62% of total C (Hao et al 2001(Hao et al , 2004Hao et al 2011).…”

Composting: An opportunity in a carbon conscious world for combating climate change

“…The effects of diet manipulation on manure properties can also carryover to affect GHG emission from manure composting. When an 85% barley grain finishing diet was replaced with 60% dried distilled grains (DDGS) and only 25% barley grain, N 2 O emissions from composting cattle manure were higher but CH 4 emissions were not affected (Hao et al, 2011). The greater N 2 O emission can be attributed to the higher N content in DDGS.…”