Assessment of potato peel and agro-forestry biochars supplementation on in vitro ruminal fermentation

Abstract

Background The awareness of environmental and socio-economic impacts caused by greenhouse gas emissions from the livestock sector leverages the adoption of strategies to counteract it. Feed supplements can play an important role in the reduction of the main greenhouse gas produced by ruminants—methane (CH4). In this context, this study aims to assess the effect of two biochar sources and inclusion levels on rumen fermentation parameters in vitro. Methods Two sources of biochar (agro-forestry residues, AFB, and potato peel, PPB) were added at two levels (5 and 10%, dry matter (DM) basis) to two basal substrates (haylage and corn silage) and incubated 24-h with rumen inocula to assess the effects on CH4 production and main rumen fermentation parameters in vitro. Results AFB and PPB were obtained at different carbonization conditions resulting in different apparent surface areas, ash content, pH at the point of zero charge (pHpzc), and elemental analysis. Relative to control (0% biochar), biochar supplementation kept unaffected total gas production and yield (mL and mL/g DM, p = 0.140 and p = 0.240, respectively) and fermentation pH (p = 0.666), increased CH4production and yield (mL and mL/g DM, respectively, p = 0.001) and ammonia-N (NH3-N, p = 0.040), and decreased total volatile fatty acids (VFA) production (p < 0.001) and H2 generated and consumed (p ≤ 0.001). Biochar sources and inclusion levels had no negative effect on most of the fermentation parameters and efficiency. Acetic:propionic acid ratio (p = 0.048) and H2 consumed (p = 0.019) were lower with AFB inclusion when compared to PPB. Biochar inclusion at 10% reduced H2 consumed (p < 0.001) and tended to reduce total gas production (p = 0.055). Total VFA production (p = 0.019), acetic acid proportion (p = 0.011) and H2 generated (p = 0.048) were the lowest with AFB supplemented at 10%, no differences being observed among the other treatments. The basal substrate affected most fermentation parameters independently of biochar source and level used. Discussion Biochar supplementation increased NH3-N content, iso-butyric, iso-valeric and valeric acid proportions, and decreased VFA production suggesting a reduced energy supply for microbial growth, higher proteolysis and deamination of substrate N, and a decrease of NH3-N incorporation into microbial protein. No interaction was found between substrate and biochar source or level on any of the parameters measured. Although AFB and PPB had different textural and compositional characteristics, their effects on the rumen fermentation parameters were similar, the only observed effects being due to AFB included at 10%. Biochar supplementation promoted CH4 production regardless of the source and inclusion level, suggesting that there may be other effects beyond biomass and temperature of production of biochar, highlighting the need to consider other characteristics to better identify the mechanism by which biochar may influence CH4 production.

Ruminal inocula with distinct fermentation profiles differentially affect the in vitro fermentation pattern of a commercial algal blend

“…In vitro rumen batch culture is a technique widely used for predicting the degradability and nutritive value of feed sources ( 23 , 24 ). It is also used to screen the potential of non-conventional additives and feeds, such as biochars, microalgae, and seaweeds ( 6 , 25 , 26 ), to modulate ruminal fermentation and, in particular, to reduce methane production. Despite its simplicity and the possibility of testing multiple samples at a single batch under similar conditions and without interference from the metabolic process of the host, several factors may influence the consistency of results ( 11 , 23 ).…”

Review: Heads or Tails? Toward a Clear Role of Biochar as a Feed Additive on Ruminant’s Methanogenesis

“…For example, the ash content that results from the decomposition of the inorganic matter of biomass [23] is expected to be low in wood-based biomass when compared to mineral-rich biomass, such as grass, manure, litter, and solid waste [36]. Wood, bamboo, corncob, corn stover, pellets (miscanthus, softwood, wheat straw, and oilseed rape straw), rice straw, and potato peel biochar reported less than 25% of ash content, while rice husk presented higher than 40% [37][38][39][40][41][42][43][44]. The ash content has been demonstrated to be relevant for the surface polarity and distribution of pores, thus influencing the sorption capacity of the material.…”

“…A comparison between studies is further complicated by the diversity of biomass sources used (e.g., rice husk, pine wood, corn stover, cashew nutshell, tree pruning, rice straw, corncob, bamboo) that might affect VFA profile, thus introducing a confounding effect on the mechanism of CH 4 reduction. Most studies that compared the impact of biomass sources on enteric CH 4 production [37,38,41,42] observed no differences among biochar sources. Conversely, Van Dung et al [44] found rice straw and bamboo biomass to reduce CH 4 production compared to corncob, at 4 and 48 h of incubation, but not at 24 h. Moreover, these authors observed an interaction effect between biomass source and pyrolysis temperature [44], supporting the need for a multi-aspect analysis of biochar's chemical and physical properties.…”

“…Conversely, Van Dung et al [44] found rice straw and bamboo biomass to reduce CH 4 production compared to corncob, at 4 and 48 h of incubation, but not at 24 h. Moreover, these authors observed an interaction effect between biomass source and pyrolysis temperature [44], supporting the need for a multi-aspect analysis of biochar's chemical and physical properties. The effects on VFA profile were further assessed [38,40,42,55,56]. In the study of Calvelo Pereira et al [38], despite a decrease in propionate proportion found with some mixtures, which might indicate an increase in H 2 produced, the effects were insufficient to affect CH 4 production.…”

“…Saenab et al [56] observed a reduction of CH 4 production by 11.5% with 3% [dry matter (DM) basis] cashew nutshell biochar supplementation, although total and individual VFA produced were unaffected. Rodrigues et al [42] attributed the reduction of VFA production through biochar addition to a reduced energy supply for microbial growth. Supplementation of tree pruning biochar up to 4% (DM basis) did not affect CH 4 or VFA content and profile [55].…”