Pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: A review

Pretreatment technologies are aimed to increase enzyme accessibility to biomass and yields of fermentable sugars. In general, pretreatment methods fall into four different categories including physical, chemical, physico-chemical, and biological. This paper comprehensively reviews the lignocellulosic wastes to bioethanol process with a focus on pretreatment methods, their mechanisms, advantages and disadvantages as well as the combinations of different pretreatment technologies. Moreover, the new advances in plant “omics” and genetic engineering approaches to increase cellulose composition, reduce cellulose crystallinity, produce hydrolases and protein modules disrupting plant cell wall substrates, and modify lignin structure in plants have also been expansively presented.

Lignocellulosic biomass to bioethanol, a comprehensive review with a focus on pretreatment

Production of bioethanol from wheat straw: An overview on pretreatment, hydrolysis and fermentation

Lignocellulosic feedstock materials are the most abundant renewable bioresource material available on earth. It is primarily composed of cellulose, hemicellulose, and lignin, which are strongly associated with each other. Pretreatment processes are mainly involved in effective separation of these complex interlinked fractions and increase the accessibility of each individual component, thereby becoming an essential step in a broad range of applications particularly for biomass valorization. However, a major hurdle is the removal of sturdy and rugged lignin component which is highly resistant to solubilization and is also a major inhibitor for hydrolysis of cellulose and hemicellulose. Moreover, other factors such as lignin content, crystalline, and rigid nature of cellulose, production of post-pretreatment inhibitory products and size of feed stock particle limit the digestibility of lignocellulosic biomass. This has led to extensive research in the development of various pretreatment processes. The major pretreatment methods include physical, chemical, and biological approaches. The selection of pretreatment process depends exclusively on the application. As compared to the conventional single pretreatment process, integrated processes combining two or more pretreatment techniques is beneficial in reducing the number of process operational steps besides minimizing the production of undesirable inhibitors. However, an extensive research is still required for the development of new and more efficient pretreatment processes for lignocellulosic feedstocks yielding promising results.

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Recent updates on different methods of pretreatment of lignocellulosic feedstocks: a review

A Short Course in Cloud Physics

Comparison of dilute mineral and organic acid pretreatment for enzymatic hydrolysis of wheat straw

Supercritical water gasification of sewage sludge: gas production and phosphorus recovery

Phosphorus was recovered from the ash obtained after combustion at different temperatures (600 °C, 750 °C and 900 °C) and after gasification (at 820 °C using a mixture of air and steam as fluidising agent) of char from sewage sludge fast pyrolysis carried out at 530 °C. Depending on the leaching conditions (extraction time, acid load and acid concentration, and type of acid) 90% mass of the original P was recovered. Regarding char combustion ash, higher phosphorus yields are obtained from ash obtained at 900 °C than at 600 °C and 750 °C when using sulphuric acid. Combustion temperature does not affect phosphorus leaching with oxalic acid. A contact time of 2 h and an oxalic acid load of 10 kg kg−1 of P seem sufficient for phosphorus extraction. Almost all phosphorus present in gasification ash is leached after 2 h with both sulphuric and oxalic acid using an acid load of 14 kg kg−1 of P. Char ash is a possible renewable source of phosphorus and it can be an alternative to rock phosphate in fertilizer production. The combination of sewage sludge pyrolysis, combustion or gasification of the char and phosphorus extraction from the final solid residue contributes to the integral exploitation of sewage sludge.

Phosphorus recovery from sewage sludge char ash.

In order to recycle phosphorus from the livestock chain back to the land, fast pyrolysis of concentrated pig manure at different temperatures (400 °C, 500 °C, 600 °C), was undertaken to concentrate the phosphorus in the char fraction for recovery. Results show that 92%–97% of the phosphorus present in the pyrolysis feedstock ends up in the char fraction, while 60%–75% of that can be directly leached as ortho-phosphate, and 90% as total phosphorus. After char combustion, 100% of the phosphorus present can be leached as ortho-phosphate from the ash. Yields, heating values, and properties of the pyrolysis products have been analyzed. Expressed per tonne of fresh pig manure, the char phosphorus value is estimated at 0.81 € t−1–0.86 € t−1, energy application value at 2.4 € t−1–3.6 € t−1 (liquid organic phase) and 0.5 € t−1–0.7 € t−1 (char), and the fertilizer value of the aqueous phase at 0.10 € t−1–0.18 € t−1. Including costs for energy requirement, solid–liquid separation, and drying, pyrolysis costs are estimated around 0.4 € t−1–4.4 € t−1 for pig manure. It is concluded that pyrolysis costs compare positively with pig manure transportation costs of 0.06 € t−1 km−1, while it also offsets phosphorus extraction from the rapidly depleting phosphate rock.

Recycling phosphorus by fast pyrolysis of pig manure: Concentration and extraction of phosphorus combined with formation of value-added pyrolysis products

A.M.J. Kootstra

Papers

Comparison of dilute mineral and organic acid pretreatment for enzymatic hydrolysis of wheat straw

Supercritical water gasification of sewage sludge: gas production and phosphorus recovery

Phosphorus recovery from sewage sludge char ash.

Recycling phosphorus by fast pyrolysis of pig manure: Concentration and extraction of phosphorus combined with formation of value-added pyrolysis products

Valorisation of Jatropha curcas: Solubilisation of proteins and sugars from the NaOH extracted de-oiled press cake