“Further progress will now rely more on more direct interventions,”
said Dr van Zijderveld, adding that these are likely to be driven by industry bodies and milk buyers. “Farmers can view carbon auditing and reducing emissions as a hurdle, and they need incentives to take on the technology that’s being developed and is now available.”
Figure 3: Increasing productivity reduces emission intensity
that produce methane or we can look to block the process of methanogenesis itself. Cargill has developed a third option, where hydrogen is re-directed
in the rumen to the more useful purpose of ammonia production, which can be used in milk production. The approach has been developed from Dr van Zijderveld’s
studies, in conjunction with research facilities and academic knowledge at Wageningen University. He investigated techniques of reducing enteric methane and looked particularly at the ability of nitrate to ‘mop up’ hydrogen. “The idea came from work in industry, where nitrate was used
in the oil industry to remove hydrogen and reduce the risk of it being combined with sulphates and producing something harmful. “Knowing that the production of hydrogen in the cow’s rumen
contributed to methane production, we decided to investigate if there would be a role for this nitrate technology in ruminant diets.” Carefully monitored work measured respiration in sheep fed a diet
Capper et al., 2009 The good news is that carbon emissions in ruminants can be
reduced. “And probably more easily than in pigs and poultry, which are sectors that are more reliant on bought-in proteins and proteins that can be used in human food. “For example, we can improve milk production from forages and
reduce the replacement rearing period. Genetics will play a role in improving the carbon-efficiency of the cow. Better health and fertility, and improved feed use with feed ingredients from more sustainable sources can reduce the carbon footprint per litre of milk produced.”
Big issue “Enteric methane is the big issue,” he added. “It’s not unique to ruminants, but it is a process and nature’s way of digesting organic matter without oxygen. The microbes degrade the organic matter, in this case, feed and particularly forages, to produce nutrients for the cow.” But this also produces hydrogen that combines with CO2
to form
methane which is then removed from the rumen by eructation - or belching. This process is known as methanogenesis. It also happens in swamps and landfills, where, in the absence of oxygen, organic matter ferments and produces methane. “Our challenge is to develop nutritional techniques that can
‘intervene’ in this process and reduce the amount of methane exhaled by the cow.” Dr van Zijderveld outlined three nutritional methane-reducing options being developed or available to the dairy sector. “One option is to reduce the fermentable substrate or change
the source for the microbes to work on in the rumen either by using a fat product, increasing dry matter intakes or by increasing the starch component in the diet.” Another technique is to eliminate methanogens – microorganisms
with nitrate included, against a control, and saw a reduction of almost a third in methane production from the group fed a diet including nitrate. This supported the continuation of this work to dairy cattle. “We recorded a significant reduction in methane emissions from
cows fed on the nitrate product and this persisted over time,” says Dr van Zijderveld. “We now have a decade of research on the product and 26 scientific publications in peer-reviewed journals on this nitrate product, including a meta-analysis.”
Dr Sander van Zijderveld presenting at Total Dairy seminar, November 22
Patented technology Cargill now holds the worldwide patent on the use of dietary nitrate in methane reduction from ruminants. The technology is used in its feed product, SilvAir®
. This is a carefully manufactured feed grade calcium
nitrate comprising 76% nitrate and 22.5% calcium, with a dry matter of 84%. The product has been extensively researched and trialled and is now authorised for use in animal feed in the EU and the UK. SilvAir®
works by ‘mopping up’ some of the hydrogen produced
in the rumen during fermentation of feedstuffs. This hydrogen would otherwise combine with CO2
to produce methane. Instead, the nitrate combines with hydrogen to produce ammonia. FEED COMPOUNDER JANUARY/FEBRUARY 2023 PAGE 31
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