Grass silage for biorefinery—A meta‐analysis of silage factors affecting liquid–solid separation

Abstract

This meta‐analysis based on 19 studies from Finland comprising 43 grass silages was undertaken to evaluate the effect of silage quality on liquid yield, liquid composition and retained compounds in liquid using four different liquid–solid separation methods. Silages were classified according to species (grass, clover or a mixture of them), additive treatment (no, biological or formic acid‐based additive) and harvest (primary growth or regrowth). A mixed model regression analysis with random study effect was used to evaluate the impact of silage characteristics on biorefinery efficiency. There was a large variation in silage quality in the data set. Silage dry‐matter concentration was the characteristic most highly correlated with liquid yield for all separation methods, and when used as an independent variable in the model, it resulted in the best predictions. The liquid–solid separation methods presented a great variation in the liquid yield, ranging from 0.26 to 0.56 when silage dry‐matter concentration was standardized to 250 g/kg. There was no effect of additive treatment and harvest in the estimation of the biorefinery potential, but species was a significant variable in predicting liquid yield for the laboratory‐scale presses with higher liquid yield for mixed grass and legume. The high correlation between silage quality and liquid yield and liquid composition provides potential to predict the biorefinery potential based on equations developed for each separation method. This information can be used to modify the silage production systems so that they best meet the requirements of a green biorefinery process.

Forage type and additive effects on fermentation quality and biorefinery performance of silages

“…Silage DM concentration was closely linked to liquid yield as previously reported by Franco et al (2019). In the current data set, liquid yield decreased by 0.02 per 10 g increase in silage DM concentration, when the less efficient PP was used (R 2 = 0.95).…”

Carrot by-product fermentation quality and aerobic spoilage could be modified with silage additives

“…In our experimental setting, the yield of liquid fraction remained very low, but that could be increased by technical solutions as demonstrated e.g. by Franco et al (2019) in preparing juice from different quality grass silages using several pressing methods.…”

Agri-energy Crops for Biogas Production Regimes

“…On the other hand, the use of only animal manure in AD also has disadvantages, and the most significant is the low ratio of carbon to nitrogen (C / N) (Neshat et al, 2017). Although manure has been identified as the basic substrate for biogas plants especially in countries with intensive livestock production (Franco et al, 2019), which causes a low yield of biogas (10 ÷ 20 m 3 /t of fresh manure), pretreatment methods, co-digestion with other biodegradable organic substrates or a combination of both should be applied. Energy crops that were mainly used as raw material in the production of biogas through AD pose a threat to their use for food in contrast to abundant amounts of lignocellulosic biomass residues from field production that have the appropriate biochemical potential of methane (BPM).…”