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Livestock-Based Farming Systems, Renewable Resources and the Environment |
Three experiments were carried out to evaluate the effect of biochar on methane production from buffered ruminal fluid in an in vitro system using cassava root meal as substrate with either potassium nitrate or urea as the NPN source.
Experiment 1: The treatments in 2*2 factorial arrangement with four replications of each treatment were: urea or potassium nitrate as NPN source; and presence or absence of 5% biochar. The quantity of substrate was 12 g DM to which was added 240 ml rumen fluid (from slaughtered buffalo) and 960 ml of buffer solution. The incubation was for 24 and 48hours with measurements of gas production, percent methane, substrate fermented and methane produced per unit substrate fermented.
Gas production, methane percentage in the gas, substrate solubilized and methane produced per unit substrate solubilized were all lowered when nitrate replaced urea as the NPN source at either 24 or 48 hours of the incubation. Addition of biochar did not affect gas production but increased the percentage DM solubilized. Methane produced and methane produced per unit substrate solubilized was lowered by 14% due to addition of biochar when urea was the NPN source but was not affected when nitrate was the source of NPN.
Experiment 2: The treatments in a 2*6 factorial with three replications were: (i) concentration of biochar (0, 1, 2, 3, 4 and 5% on DM basis); (ii) washing or no washing of the biochar. The substrate was cassava root meal and urea. The general procedure and analyses were similar to those in experiment 1.
Methane produced was reduced by 11-13% by adding 1% biochar but there were no further benefits from increasing the biochar level to between 2 and 5%. Methane production and per unit substrate DM solubilized were reduced by about 5% by washed compared with unwashed biochar
Experiment 3: The design was a completely randomized comparison of: No biochar with urea, 0.5% biochar with urea, 1.0% biochar with urea, 1.% biochar with 50% urea and 50% nitrate and 1% biochar with 100% nitrate..
Biochar at 0.5% reduced methane by 10% and at 1% reduced it by 12.7%. With 50% nitrate N and 50% urea N, plus biochar at 1%, the reduction in methane was 40.5% and with 100% nitrate N plus biochar at 1%, it was 49%.
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| Figure 1. Effect of biochar and potassium nitrate or urea as NPN source on methane production per unit of substrate DM solubilized after 24 hours of fermentation | Figure 2. Effect of level of biochar on methane production after 24 hours of fermentation | Figure 3. Effect of level of biochar (0, 0.5 or 1%) with urea, or 1% biochar with combinations of urea and nitrate, on methane production per unit DM solubilized after 24 hours of fermentation |