Monitoring initial effects of the addition of biochar to cattle feed and its impact on cattle gut and soil microbiomes, with a focus on the impact to methanogens.

Current agricultural practices have a significant impact on climate change primarily through greenhouse gas emissions. Ruminants are responsible for 96% of the methane emissions in agriculture making them a key target for emission reduction efforts. Biochar has been identified as a feed additive with the potential to reduce ruminant methane emissions. This thesis focuses on methanogens (methane producing archaea), this group of archaea have been chosen as the focus of this pilot study due to biochar's potential to mitigate their activity.

Biochar is a carbon rich substance produced through pyrolysis of organic materials. In this study, the biochar used was derived from agricultural waste. Biochar is extremely carbon rich, with a porous structure containing many minerals. Biochar's structure and chemical makeup can have various positive impacts on soil, such as increasing carbon sequestration (and thereby increasing soil organic carbon levels), which can enhance soil structure, water retention, and nutrient availability, it also produces a favourable environment for beneficial microbes. Biochar is also being studied as a feed additive for cattle. The impact of biochar on the gastrointestinal tract is the subject of ongoing research, however several benefits have been suggested. It is hypothesised that with in the gastrointestinal tract of cattle and other ruminants' biochar can act as an electron acceptor reducing the reliance of carbon dioxide which plays a vital role in the production of methane.

This thesis is a preliminary study examining the impact of biochar on methanogens, as a reduction in methanogen populations has the potential to result in a decrease in methane emissions over time. Ruminant gastrointestinal as well as soil methanogen populations are to be monitored via monthly sampling over a four month time period as part of a broader longitudinal study spanning several years. Monitoring will be done by extracting DNA from the faecal and soil samples for them to be Sanger and Illumina sequenced to discover the prevalent genus, as well as to discover how these genus populations change over time.

This thesis outlines and has established the protocols to be used in order to identify changes that may occur to the genus' and abundance of methanogens found in cattle stool and soil samples. The information gathered within this thesis will be the baseline used to continuously monitor changes that have occurred due to the continuous addition of biochar over the longitudinal study.

Here it was discovered that the dominant species of methanogen found across all timepoints for both the stool and soil samples is Methanobrevibacter. Whilst Methanobrevibacter was the dominant species of methanogen found in stool samples across all timepoints using the data gathered from NCBI BLAST we see that a reduction of this species does occur. The Methanobrevibacter sp. accounted for 60% of the species observed in the T0 samples, down to 37.8% at T3. Despite of this, due to the short time frame of this pilot study it is still hard to draw conclusions from this data however, samples will be closely monitored over the upcoming years to produce a more reliable timeframe.