Piggery manure estimation and measurement for methane recovery in Australia

Abstract

Uncovered effluent treatment lagoons generate greenhouse gas and odor emissions causing community amenity impacts. Pig production facilities are generally increasing in size where energy recovery becomes economically viable. The current manure prediction models and methods are Pig-Bal, National Environmental Guidelines for Piggeries (NEGP) Department of Climate Change (DCC), International Panel on Climate Change (IPCC) and ASABE standards 2003 ASAE D384.1 and 2005 ASAE D384.2. The three case studies to compare the approaches are a medium farrow-to-finish piggery (4, 591 pigs), small grower-finisher piggery (1, 000 pigs) and large conventional grower-finisher piggery (26, 568 pigs) in Australia according to animal production, feed type and amount fed. The models and methods are compared with actual on site measurement of volatile solids (VS), total solids (TS) and nitrogen (N). For the medium piggery, Pig-Bal is the best estimator of VS, followed by ASABE 2005, DCC, NEGP and IPCC, and ASAE 2003. For the small piggery, the best VS estimation is provided by DCC, IPCC, NEGP, ASABE 2005, Pig-Bal and ASAE 2003. For the large piggery, the VS model ranking is Pig-Bal, DCC, ASABE 2005, NEGP, IPCC and ASAE 2003. For nitrogen at large piggery, the order is NEGP, ASAE 2003, Pig-Bal and ASABE 2005. Pig-Bal provides good estimate of VS at medium and large piggeries when accurate production and feed data is supplied. Other methods are comparatively useful when based on feed digestibility and intake. Further studies will enable improved validation of Pig-Bal and more accurate estimates of manure production to improve sizing and design of methane capture systems.