Effect of additives on process stability of mesophilic anaerobic monodigestion of pig slaughterhouse waste

The effect of two additives on anaerobic monodigestion of pig slaughterhouse waste was studied in three laboratory scale continuously stirred tank reactors (CSTRs) operated for 242-284 days at 35°C. A higher organic loading rate (OLR), namely 2.25 kg volatile solids (VS)/m(3)d with a hydraulic retention time (HRT) of 30 d was feasible with an additive containing Fe, HCl and trace elements while an OLR of 1.5 kg VS/m(3)d (HRT 30 d) led to instabilities in CSTR with an additive consisting of Fe and HCl and in CSTR without additives. Methane yields of ca. 700 dm(3) CH(4)/kg VS(fed) were obtained in all reactors under stable conditions. Both additives decreased H(2)S concentration of the biogas…

Hydrogen and methane yields of untreated, water-extracted and acid (HCl) treated maize in one- and two-stage batch assays

Abstract In the present study, two-stage H 2 and CH 4 production was compared with one-stage CH 4 production from maize subjected to water extraction and acid (HCl) treatment. In addition, the effect of duration (2 and 14 days) of the first-stage H 2 process on the H 2 yields and subsequent CH 4 yields from the second-stage was also investigated. Results showed that the average H 2 yields from untreated maize were 5.6 and 9.9 ml/g volatile solids added (VS added ) after 2 and 14 days, respectively. On the other hand, H 2 yields from water-extracted and HCl-treated maize were 18.0 and 20.5 ml/gVS added (14 d), respectively. On comparison to one-stage CH 4 assays, the average increase in CH 4…

Batch dark fermentative hydrogen production from grass silage: The effect of inoculum, pH, temperature and VS ratio

Abstract The potential for fermentative hydrogen (H2) production from grass silage was evaluated in laboratory batch assays. First, two different inocula (from a dairy farm digester and digested sewage sludge) were studied with and without prior heat treatment and pH adjustment. Only the inoculum from the dairy farm digester produced H2 from grass silage. Without heat treatment, methane (CH4) was mainly produced, but heat treatment efficiently inhibited CH4 production. pH adjustment to 6 further increased H2 production. The effects of initial pH (4, 5 and 6), temperature (35, 55 and 70 ∘ C ) and the substrate to inoculum volatile solids (VS) ratio (henceforth VS ratio) (1:1; 1.5:1 and 2:1) …

The effect of organic loading rate and retention time on hydrogen production from a methanogenic CSTR.

Abstract The possibility of shifting a methanogenic process for hydrogen production by changing the process parameters viz., organic loading rate (OLR) and hydraulic retention time (HRT) was evaluated. At first, two parallel semi-continuously fed continuously stirred tank reactors (CSTR) were operated as methanogenic reactors (M1 and M2) for 78 days. Results showed that a methane yield of 198–218 L/kg volatile solids fed (VS fed ) was obtained when fed with grass silage at an OLR of 2 kgVS/m 3 /d and HRT of 30 days. After 78 days of operation, hydrogen production was induced in M2 by increasing the OLR from 2 to 10 kgVS/m 3 /d and shortening the HRT from 30 to 6 days. The highest H 2 yield …

Storing energy crops for methane production: Effects of solids content and biological additive

The effect of storage on chemical characteristics and CH4 yield (taking into account loss of VS during storage) of a mixture of grasses and ryegrass, ensiled as such (low solids content) and after drying (medium and high solids) with and without biological additive, were studied in field and laboratory trials. Up to 87% and 98% of CH4 yield was preserved with low solids grass (initial TS 15.6%) and high solids ryegrass (initial TS 30.4%), respectively, after storage for 6months, while under suboptimal conditions at most 37% and 52% of CH4 yield were lost. Loss in CH4 yield was mainly due to VS loss, presumably caused by secondary fermentation as also suggested by increasing pH during storag…

Screening for potential fermentative hydrogen production from black water and kitchen waste in on-site UASB reactor at 20 degrees C.

The potential of black water and a mixture of black water and kitchen waste as substrates for on-site dark fermentative hydrogen production was screened in upflow anaerobic sludge blanket reactors at 20 degrees C. Three different inocula were used with and without heat treatment. With glucose, the highest specific hydrogenogenic activity was 69 ml H2 g volatile solids(-1) d(-1) in batch assays and the highest hydrogen yield 0.44 mol H2 mol glucose(-1) in upflow anaerobic sludge bed reactor. The mixture of black water and kitchen waste degraded readily into volatile fatty acids in the reactors, thus showing potential for hydrogen production. In the conditions applied, however, the highest en…

One-stage H2 and CH4 and two-stage H2+ CH4 production from grass silage and from solid and liquid fractions of NaOH pre-treated grass silage

Abstract In the present study, mesophilic CH4 production from grass silage in a one-stage process was compared with the combined thermophilic H2 and mesophilic CH4 production in a two-stage process. In addition, solid and liquid fractions separated from NaOH pre-treated grass silage were also used as substrates. Results showed that higher CH4 yield was obtained from grass silage in a two-stage process (467 ml g−1 volatile solids (VS)original) compared with a one-stage process (431 ml g−1 VSoriginal). Similarly, CH4 yield from solid fraction increased from 252 to 413 ml g−1 VSoriginal whereas CH4 yield from liquid fraction decreased from 82 to 60 ml g−1 VSoriginal in a two-stage compared to …

Methane and hydrogen production from crop biomass through anaerobic digestion

Biogas from energy crops--optimal pre-treatments and storage, co-digestion and energy balance in boreal conditions.

The objective of this research was to evaluate the biogas production from crops in boreal conditions, focusing on the optimal pre-treatment and storage methods, co-digestion and energy balance of farm-scale crop based biogas plants. Alkaline treatments offered some potential for improving the methane yield from grass and sugar beet tops. The results show that the CH4 yield of energy crops can be maintained by appropriate ensiling conditions for even after 11 months in ambient conditions. The CH4 yield was best preserved with wet grass mixture without additives. Co-digestion of manure and crops was shown to be feasible with feedstock volatile solids (VS) containing up to 40% of crops. The hi…