Anaerobic digestion of biomass for methane production: a review

Biological conversion of biomass to methane has received increasing attention in recent years. Hand- and mechanically-sorted municipal solid waste and nearly 100 genera of fruit and vegetable solid wastes, leaves, grasses, woods, weeds, marine and freshwater biomass have been explored for their anaerobic digestion potential to methane. In this review, the extensive literature data have been tabulated and ranked under various categories and the influence of several parameters on the methane potential of the feedstocks are presented. Almost all the land- and water-based species examined to date either have good digestion characteristics or can be pre-treated to promote digestion. This review emphasizes the urgent need for evaluating the inumerable unexplored genera of plants as potential sources for methane production.

Anaerobic digestion of biomass for methane production: A review

The last 15 years of hydroformylation and carbonylation chemistry are reviewed, including technical and commercial aspects.

Progress in hydroformylation and carbonylation

Anaerobic digestion is a well established process for treating many types of organic waste, both solid and liquid. As such, the digestion of cattle slurries and of a range of agricultural wastes has been evaluated and has been successful. Previous batch studies have shown that based on volatile solids (VS) reduction, total methane production and methane yield, co-digestions of cattle slurry (CS) with fruit and vegetable wastes (FVW) and with chicken manure (CM) were among the more promising combinations. A continuously stirred tank reactor ( 18 litres ) was used as a mesophilic (35°C) anaerobic reactor to examine the effect of adding the FVW and CM to a system which was digesting CS. The retention time was kept at 21 days and the loading rate maintained in the range 3.19– 5.01 kg VS m −3 d −1 . Increasing the proportion of FVW from 20% to 50% improved the methane yield from 0.23 to 0.45 m 3 CH 4 kg −1 VS added, and caused the VS reduction to decrease slightly. Increasing the proportion of chicken manure in the feed caused a steady deterioration in both the criteria for judging digester performance. This appeared to be caused by ammonia inhibition.

Continuous co-digestion of cattle slurry with fruit and vegetable wastes and chicken manure

Bioreactor performance in anaerobic digestion of fruit and vegetable wastes

Two-phase anaerobic digestion of a mixture of fruit and vegetable wastes

Results of a two-phase mesophilic (35°C) anaerobic digestion treatment of fruit and vegetable wastes, carried out at laboratory scale, are presented and discussed. They are contrasted with other results obtained with a similar waste, but digested in a one-phase system. The yields are lower in this simple two-phase system, because of the higher organic loading rate. It is concluded that this two-phase system does not seem appropriate to treat these wastes unless it is equipped with some type of control of the hydrolytic step. A one-phase system is simpler and can yield at least the same yields.

Two-phase continuous anaerobic digestion of fruit and vegetable wastes

Anaerobic digestion of a simulated organic fraction of the waste of a central market selling fruit and vegetables was carried out in two-phase digesters in the mesophilic range of temperatures. Batch digestion was prolonged until no biogas was produced (33 days). With digested pig manure as inoculum, maximum biogas production was obtained around day 10, and within 3 weeks the digestion was almost complete. A kinetic analysis was carried out using first-order, Monod and Chen-Hashimoto models. The Chen-Hashimoto model represents the best fit, whereas a first-order model was not consistent with the experimental results.

Kinetic and performance study of a batch two-phase anaerobic digestion of fruit and vegetable wastes

In this paper the results of volatile fatty acids (VFA) production from the hydrolysis of fruit and vegetable wastes are presented. Experiments were conducted at laboratory scale reactors (130 cm3). pH was controlled at the desired level in order to study its influence. High yields were obtained (up to 40 g VFA 1−1) at the optimum pH, which resulted in the range of 6.4–6.6. A first order kinetic model fitted quite well to the degradation rate. A mathernathical expression relating the first order kinetic constant with pH was also deduced.

Chemicals production from wastes

A mathematical model to represent the two-phase anaerobic digestion of a mixture of fruit and vegetable wastes is presented. The hydrolytic phase is represented by a first order model and the methanization phase by a Monod one. The first order constant and the yield coefficient are taken from other fitting studies performed with the same substrate. The values of μ max and the saturation constant are fitted from the results of a discontinuous two-phase digestion. μ max is fitted as a pH-dependent constant. The model is validated with the results obtained by a continuous two-phase digestion carried out with the same substrate

A. Mtz.-Viturtia

Papers

Two-phase anaerobic digestion of a mixture of fruit and vegetable wastes

Two-phase continuous anaerobic digestion of fruit and vegetable wastes

Kinetic and performance study of a batch two-phase anaerobic digestion of fruit and vegetable wastes

Chemicals production from wastes

Two-Phase Kinetic Model Fitting in a Two-Phase Anaerobic Digestion of Highly Biodegradable Organic Matter