Effects of Hardwood Biochar on Methane Production, Fermentation Characteristics, and the Rumen Microbiota Using Rumen Simulation

Rebecca Teoh; Eleonora Caro; Devin B Holman; Stephen Joseph; Sarah J Meale; Alex V Chaves

doi:10.3389/fmicb.2019.01534

Effects of Hardwood Biochar on Methane Production, Fermentation Characteristics, and the Rumen Microbiota Using Rumen Simulation

Front Microbiol. 2019 Jul 10:10:1534. doi: 10.3389/fmicb.2019.01534. eCollection 2019.

Authors

Rebecca Teoh¹, Eleonora Caro^{2

3}, Devin B Holman⁴, Stephen Joseph⁵, Sarah J Meale⁶, Alex V Chaves²

Affiliations

¹ Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camperdown, NSW, Australia.
² School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown, NSW, Australia.
³ Department of Agricultural, Forestry and Food Science, University of Turin, Turin, Italy.
⁴ Lacombe Research and Development Centre, Agriculture and Agri-Food Canada, Lacombe, AB, Canada.
⁵ School of Materials Science and Engineering, University of New South Wales, Sydney, NSW, Australia.
⁶ School of Agriculture and Food Sciences, Faculty of Science, The University of Queensland, Gatton, QLD, Australia.

Abstract

Biochar is a novel carbonized feed additive sourced from pyrolyzed biomass. This compound is known to adsorb gasses and carbon, participate in biological redox reactions and provide habitat biofilms for desirable microbiota proliferation. Therefore, biochar holds potential to modify rumen fermentation characteristics and reduce enteric CH₄ emissions. The objective of this study was to investigate the effect of hardwood biochar supplementation on fermentation parameters, methane (CH₄) production and the ruminal archaeal, bacterial, and fungal microbiota using the in vitro RUSITEC (rumen simulation technique) system. Treatments consisted of a control diet (oaten pasture: maize silage: concentrate, 35:35:30 w/w) and hardwood biochar included at 400 or 800 mg per day (3.6 and 7.2% of substrate DM, respectively), over a 15-day period. Biochar supplementation had no effect (P ≥ 0.37) on pH, effluent (mL/d), total gas (mL/d), dry matter (DM) digestibility or CH₄ production (mg/d). The addition of 800 mg biochar per day had the tendency (P = 0.10) to lower the % of CH₄ released in fermentation compared to 400 mg/d biochar treatment. However, no effect (P ≥ 0.44) was seen on total VFA, acetate, propionate, butyric, branched-chain VFA, valerate and caproate production and the ratio of acetate to propionate. No effect (P > 0.05) was observed on bacterial, archaeal or fungal community structure. However, biochar supplementation at 800 mg/d decreased the abundance of one Methanomethylophilaceae OTU (19.8-fold, P = 0.046) and one Lactobacillus spp. OTU (31.7-fold, P < 0.01), in comparison to control treatments. Two fungal OTUs classified as Vishniacozyma victoriae (5.4 × 10⁷ increase) and Sporobolomyces ruberrimus (5.4 × 10⁷-fold increase) were more abundant in the 800 mg/d biochar samples. In conclusion, hardwood biochar had no effects on ruminal fermentation characteristics and may potentially lower the concentration of enteric CH₄ when included at higher dosages by manipulating ruminal microbiota abundances.

Keywords: 16S rRNA gene abundance; RUSITEC system; fungal ITS1 region; pyrolyzed biomass; ruminant feeds.