Objective Leader - Dr David Pacheco (AgResearch) 



Practical strategies to reduce agricultural greenhouse gas emissions are urgently sought, particularly for ruminant enteric methane, which forms 31% of New Zealand&#39;s total greenhouse gas inventory (Pinares-Patino et al, 2009).  The most successful strategies will be those that lead to a profitable increase in animal productivity, as well as reducing net greenhouse gas emissions, not just those of enteric methane alone. 


Dietary fat supplements, especially those containing unsaturated fatty acids, can reduce enteric methane emissions, but oil production for animal feed is usually associated with increased net greenhouse gas emissions (Beauchemin et al, 2008, 2009; Grainger et al, 2010).  Eicosahexanoic acid (EPA or C20:5) and Docosahexanoic acid (DHA or C22:6) are the major bioactive unsaturated fatty acids found in fish oil and marine algae (Givens et al, 2000).  In-vitro studies suggest that EPA and DHA may reduce methane emissions by up to 80% (Fievez et al, 2003) and marine algae by greater than 92% (Bozic et al, 2009).  


A commercial DHA microalgae supplement has been shown to reduce dry matter intake and increase milk yield of dairy cows (Boeckaert et al, 2008).  Seaweeds and algae are more digestible than many terrestrial plants, due to less cellulose and more starch.  However, in-vivo trials feeding algae or algae products where methane emissions have been measured have not yet appeared in the peer-reviewed literature, although it is understood these are underway in Australia (Chris Grainger, pers comm., Tony Parker, pers comm.). 


Microalgae offer a means of supplementing animals with a source of unsaturated fatty acids with believed potent methane mitigation potential that will reduce net greenhouse gas emissions.  Microalgae of freshwater and marine origin can be cultivated to treat wastewaters of human, agricultural and industrial origin e.g. from sewage and effluents from dairy farms, piggeries, aquaculture facilities and fossil fuel fired power stations.  


New Zealand research by NIWA has developed wastewater treatment high rate algal ponds and there are several demonstration facilities that could provide sufficient biomass for harvest and potential use as a methane-mitigating animal feed supplement.  Meanwhile, in Australia, researchers at James Cook University (T. Parker and R. de Nys) have been attempting to feed marine macroalgae cultivated in the University algal farm to cattle to reduce methane emissions.  However, they have recently moved to producing freshwater microalgae to avoid suspected iodine toxicity in cattle initially fed algae of marine origin.  These researchers are also to test a microalgal meal, a bi-product from microalgal oil production from a bio-sequestration ‘algal synthesiser&#39; farm associated with a coal-fired power station, for methane mitigation potential in cattle (T. St Clair and T. Parker, pers comm.). 


This project capitalises on these very recent developments to keep New Zealand at the forefront of enteric methane mitigation research.  Microalgal supplements of NZ and Australian origin will be evaluated for methane mitigation potential in sheep using the ‘gold-standard&#39; calorimetry facility at AgResearch.  If successful, we may have a nutrition supplement capable of both reducing methane emissions and enhancing animal production, at a reduction in net greenhouse gas emissions. 


1.1 - Progress in 2009/2010 


An international review of the literature of the potential of micro- and macro-algae or algae bi-products such as oil or meal as feed supplements for reducing ruminant enteric methane emissions has been initiated.  This has included sourcing information on algae of fresh water and marine origin.  The review will include the chemical composition of algal biomass for enteric methane emission reduction and the risks to animal health from feeding wastewater-grown algae. 


Initial samples of algal biomass grown in NIWA&#39;s domestic wastewater treatment ponds at Ruakura have been shown to contain 20-30% total lipid, with results for individual fatty acids pending.  Further sampling over the next 4 months will also include the algae from NIWA designed ponds at DairyNZ, Hamilton and Christchurch wastewater treatment plant and will also be analysed for polyunsaturated fatty acid composition of the total lipid, in addition to all other aspects of chemical composition and toxicology (Massey University).  From this, the three NZ sources of microalgae can be compared and any risks to animal health from feeding these sources of algae can be identified.  In October, the best source of algae for feeding to sheep will be identified so that the required quantities can be collected before the animal trial commences in January 2011. 


Initial discussions have been held with Australian researchers (James Cook University) on similar trials that they have already conducted supplementing the diet of cattle with macroalgae harvested from a coastal lagoon. 


1.1 - Progress in 2010/2011 


The objectives of this programme have been fully achieved after some modifications to the original milestones.  Microalgae from two waste water ponds and two marine algae of NZ origin were grown, collected, and analysed for fatty acid and lipid composition.  The two samples with the highest lipid concentrations were then tested in the laboratory for their ability to reduce CH4 emissions.  No reduction in emissions was recorded, probably because the level of lipids in these samples was too low to reproduce the results from other studies demonstrating that feeds with a high lipid content can decrease CH4 emissions.  This work was therefore discontinued.  An alternative algal species was incubated with ryegrass in an in-vitro batch test and this reduced CH4 production.  The next stage of this work will be to repeat the work under the more realistic conditions of a continuous culture test and to further assess the practicalities of using marine algae like this as CH4 mitigation agents.  The next stage of this work will be carried out under the MITIGAS component of an AgResearch SLMACC funded programme. 


DISCLAIMER:  The above reports have not been peer reviewed and report interim results only.  Therefore, they may be subject to change.