Good science for improving policy: greenhouse gas emissions from agricultural manures

Abstract

Abstract. Australia's and New Zealand's major agricultural manure management emission sources are reported to be, in descending order of magnitude: (1) methane (CH 4 ) from dairy farms in both countries; (2) CH 4 from pig farms in Australia; and nitrous oxide (N 2 O) from (3) beef feedlots and (4) poultry sheds in Australia. We used literature to critically review these inventory estimates. Alarmingly for dairy farm CH 4 (1), our review revealed assumptions and omissions that when addressed could dramatically increase this emission estimate. The estimate of CH 4 from Australian pig farms (2) appears to be accurate, according to industry data and field measurements. The N 2 O emission estimates for beef feedlots (3) and poultry sheds (4) are based on northern hemisphere default factors whose appropriateness for Australia is questionable and unverified. Therefore, most of Australasia's key livestock manure management greenhouse gas (GHG) emission profiles are either questionable or are unsubstantiated by region-specific research. Encouragingly, GHG from dairy shed manure are relatively easy to mitigate because they are a point source which can be managed by several 'close-to-market' abatement solutions. Reducing these manure emissions therefore constitutes an opportunity for meaningful action sooner compared with the more difficult-to-implement and long-term strategies that currently dominate agricultural GHG mitigation research. At an international level, our review highlights the critical need to carefully reassess GHG emission profiles, particularly if such assessments have not been made since the compilation of original inventories. Failure to act in this regard presents the very real risk of missing the 'low hanging fruit' in the rush towards a meaningful response to climate change.

Mitigation of Greenhouse Gas Emissions from Tropical Soils Amended with Poultry Manure and Sugar Cane Straw Biochars

“…According to [41], the waste management is one of the principle causes of GHG emissions in the agricultural environment, which corroborates the loss of C and N after the application of these residues to soil. The higher emission of N 2 O (Figure 3(a)) for the 25 Mg•ha −1 rate of applied PM (the only one that differs statistically from the control) was attributed to a combination of oxygen and C availability.…”

Investigating Low-Carbon Agriculture: Case Study of China’s Henan Province

“…To estimate CO 2 emissions caused by farmers engaged in agricultural production activities, three types of greenhouse gases are examined in this paper: CO 2 , CH 4 , and N 2 O [3]. Academics generally believe that agricultural carbon emissions mainly come from the following sources: carbon emissions caused by agricultural material inputs; agricultural land use energy consumption, land tilling, agricultural waste treatment, and other aspects involving carbon emissions [46]; CH 4 and other greenhouse gas emissions generated from rice growth [11,47]; N 2 O emissions due to soil surface damage [48]; and livestock breeding emissions, including CH4 emissions from enteric fermentation and CH 4 and N 2 O emissions triggered by manure management [11,15,49].…”

“…These affect climate change [2]. Agriculture is also a major source of GHGs, mostly comprised of CO 2 , N 2 O, and CH 4 [3]. Rapid agricultural development has become an important factor contributing to climate change and global warming.…”

Soil N availability, rather than N deposition, controls indirect N2O emissions

“…Within the inventory guidelines (IPCC, 2006) there is recognition that low deposition rates lead to low indirect emissions rates (based on measurements from low ammonia depositions in Canada; Corre et al, 1999), and a lower emission factor may be appropriate (page 11.24, IPCC, 2006). The accuracy of this approach for varied agricultural systems in other locations is unknown, and all of the cited studies assumed ammonia deposition rates based on literature values (Pratt et al, 2015). However, actual measurement of ammonia deposition rates suggests that these rates exhibit large spatial variability.…”