Digestion Of Stover Research Articles

Fates of Heavy Metals in Anaerobically Digesting the Stover of Grain Sorghum Harvested from Heavy Metal-Contaminated Farmland

Two varieties of grain sorghum, including Chuannuo (CN) and Luzhouhong (LZH), were attempted on heavy metal (HM−) contaminated farmland. HMs distribution in the harvested biomasses, including grain and stover (leaf + stalk), were analyzed. The mostly HM-accumulated part was anaerobically digested to check the biogas releasing performances, and the fates of HMs in digestion. Results indicated the bioconcentration factors were lower than 1, suggesting these investigated varieties were characterized by lower accumulation on HMs. The accumulated HMs mainly existed in stover, in detail, 80.9% (Cu), 71.4% (Pb), 97.8% (Cr) and 99.1% (Cd) were in CN, and the corresponding HM was 78.4%, 85.1%, 98.9% and 97.8%, respectively, in LZH. Anaerobic digestion of stover were performed well with methane yield of 173.78 mL/g VS and 144.73 mL/g VS for CN and LZH, respectively. After digestion, more than 99% HMs were retained in solid residues, in which the residual state HMs were increased by 7–38%. Besides, the decreased mobility (except Cu) and bioavailability after anaerobic digestion implied these HMs tended to be more stable in the digested solid residues.

Influence of recirculation of liquid fraction of the digestate (LFD) on maize stover anaerobic digestion

Influence of recirculation of the liquid fraction of the digestate (LFD) on anaerobic digestion of maize stover as sole substrate was investigated. Digestion without recirculation (R1) was compared with two LFD recirculation modes, direct recirculation (R2) and aerated recirculation (R3). There were no significant differences in biomethane production, biomethane yield, substance reduction rates, and pH. The biomethane yield in R1, R2, and R3 reached 73.8%, 68.2%, and 71.8% of the theoretical methane potential (TMP), respectively, and 55–60% of cellulose and hemicellulose were converted into biogas in three runs. Chemical oxygen demand (COD) and ammonia nitrogen (NH3–N) concentrations gradually increased in R2 over the whole period of digestion (360 days), but stabilised in R1 and R3 by the end of the digestion (225th−360th day). Aerated recirculation performed best in terms of COD reduction, and low NH3–N accumulation for long term operation, and therefore is recommended. The study indicated that it is technically acceptable to partially recirculate the liquid fraction for anaerobic digestion of maize stover, with the potential to reduce LFD discharge and avoid potential pollution associated with LFD.

Effect of addition of leaves from Combretum aculeatum and Leucaena leucocephala on digestion of Sorghum stover by sheep and goats

A series of four digestibility trials, each with four local adult castrated sheep and goats, conducted in Burkina Faso, confirmed the superiority of goats in using the low quality roughage chopped sorghum stover. Goats ingested less DM, but through selection and better digestion they absorbed more OM than sheep. A diet with 30% Combretum aculeatum was as digestible as one with supplementation from agro-industrial by-products but the first allowed the absorption of more OM, especially by goats. The ration with 30% Leucaena leucocephala was not as digestible and the diet with 10% Leucaena leucocephala did not provide maintenance requirements. Refusal of chopped Sorghum bicolor stovers decreased if it was supplemented with 30% dried tree leaves, which are more available to farmers than agro-industrial by-products. Utilization of browse species in ruminant nutrition will contribute to the durability of the mixed agricultural production system through more intensive recycling of cereal crop residues.

Upgrading of sorghum stover with anhydrous ammonia or urea treatments

The effects of anhydrous ammonia and urea treatments of sorghum stover on intake, in vivo digestibility, in situ dry matter degradation and nitrogen balance on sheep were compared. Untreated, ammonia-treated (3% dry matter (DM) basis) and urea-treated (5.3% and 25% water, DM basis) stovers were fed ad libitum to four sheep, supplemented with 300 g of barley and 30 g of a mineral/vitamin mix for 25 days. Both treatments resulted in a smaller decrease in the fibre content of stover, but total nitrogen contents were markedly increased with urea (18.9% of DM) and ammonia (17.0% of DM) treatments compared with untreated stover (9.3% of DM). The free ammonia nitrogen and the fibre-bound nitrogen (N-NDF) contents were increased by the ammonia (+2.4 g kg −1 and +0.6 g kg −1 DM, respectively) and the urea (+4.4 g kg −1 and +0.4 g kg −1 DM) treatments. Ammonia treatment resulted in an increase in the DM intake from 31.4 g DM kg −1 W 0.75 for untreated stover to 47.2 g DM kg −1 W 0.75; urea treatment increased DM intake to 46.8 g DM kg −1 W 0.75. Organic matter, fibre and crude protein digestibilities were increased when stover was treated. The highest crude protein digestibility and nitrogen retention values were obtained with the urea treatment (66.6% and 6.2 g day −1 respectively), while the highest fibre digestibility (NDF) value was recorded with the ammonia treatment (65.1%). Rumen cellulolytic activity measured as in situ dry matter degradation showed the same pattern of variation as in in vivo fibre digestibility. Ammonia and urea treatments increased the potentially degradable fraction from 61.4% for untreated stover to 80.1% and 68.4% respectively. The rate of degradation also increased from 2.88% h −1 for untreated stover to 2.92% h −1 and 3.67% h −1, respectively, with ammonia and urea treatments. Both anhydrous ammonia and urea treatments increased the intake and digestion of sorghum stover by sheep. Urea is as effective as anhydrous ammonia in improving the nutritive value of sorghum stover.

Feeding sorghum stover to Ethiopian sheep: effect of stover variety and amount offered on growth, intake and selection

Wahed and Owen (1986) showed that intake of barley straw by goats increased when the amount of straw offered was increased from 18 to 54 and 90 g dry matter (DM) per kg mass (M) daily. The three offer rates were associated with refusal rates (% of offer) of 14, 57 and 70 % respectively. Subsequent work at Reading by Allmon et al (1989) indicated that goats were selecting more straw-leaf when offer rates were Increased.The present study, undertaken in Ethiopia, investigated whether similar responses would occur with sheep offered increasing quantities of sorghum stover (straw) and whether the responses would vary according to variety of sorghum. Dry-land farmers In Ethiopia and other African countries are being encouraged to plant new varieties of sorghum which are more bird-resistant than the traditional varieties. Unfortunately bird-resistant varieties have been shown to contain polyphenolic compounds which may have adverse effects on intake and digestion of stover. Two contrasting varieties of stover were therefore compared in the present study.

Effect of Branched Chain Volatile Fatty Acids, Trypticase,® Urea, and Starch on In Vitro Dry Matter Disappearance of Soybean Stover

We measured in vitro effects of branched chain fatty acids, Trypticase® (a pancreatic digest of casein, a bacteriological peptone),2 urea, starch, and their interactions on dry matter disappearance of soybean stover. Quantities of nutrients added to fermentation media were equal to amounts of nutrients contributed by one part alfalfa added to two parts soybean stover. Maximum digestibilities were between 48 and 56h except when branched chain fatty acids and Trypticase® were added to the medium together. In this case, a linear increase in digestion occurred even at 72h. There was a negative effect of starch and a positive effect of branched chain fatty acids on in vitro dry matter disappearance of soybean stover. Neither Trypticase® nor urea had any effect on digestion of soybean stover. Among the interactions, only the interaction between branched chain fatty acids and starch was significant, indicating either the negative effect of starch on utilization of branched chain fatty acids or utilization of branched chain fatty acids and starch by rumen microorganisms at the expense of fiber. Branched chain fatty acids and Trypticase® together appeared to provide a balanced medium for bacterial growth.