In-situ pyrogenic production of biodiesel from swine fat

Valorization of aflatoxin contaminated peanut into biodiesel through non-catalytic transesterification

Aflatoxins (AFs) are the extremely hazardous metabolites (carcinogens) that are sporadically observed in crops, and these toxic chemicals are indeed lethal to the health of living organisms including human beings. Thus, AF contaminated food waste needs to be disposed as an environmentally benign way, not releasing it into the environment. This study offered a sustainable disposal and valorization platform for AF contaminated food. Peanut was used as a model food waste, because AF is readily appeared in the peanut during its harvesting, cultivation, storage, transportation process. As the valorization platform, non-catalytic transesterification of AF contaminated peanut was employed to convert it to biodiesel (BD). From the process, lipid in AF contaminated peanut is converted into BD (95.2 wt% yield) at 365°C for 1 min. Since the boiling points of BD and AF are significantly different, this process could also resolve the separation problem of AF (180 °C) from BD (≥ 330 °C) during the transesterification reaction. As a comparison study, alkali-catalyzed reaction was done. The alkali-catalyzed one required a pretreatment process to extract peanut oil for transesterification. The highest yield was 67.8 wt% yield after 6 h of reaction at 65 °C.

Catalytic pyrolysis of swine manure using CO2 and steel slag

Pyrolysis of swine manure (SM) was conducted as a case study to establish an environmentally sound management of livestock manure. To build a more renewable pyrolysis platform for SM, this study selected carbon dioxide (CO₂) as the reaction medium. In addition, CO₂ was used in pyrolysis of SM to restrict the formation of toxic compounds, such as benzene derivatives and polycyclic aromatic hydrocarbons (PAHs). A series of thermo-gravimetric analysis (TGA) tests was done to understand the thermolysis of SM in the CO₂ environment. The TGA tests elucidated no occurrence of heterogeneous reactions between the SM sample and the CO₂. Moreover, the TGA tests of SM suggested that SM contains more volatile matter (VM) than lignocellulosic biomass. Non-catalytic transesterification of SM lipids confirmed that the dried SM sample contained 8.85 ± 0.05 wt% of lipids. This study also confirmed that the mechanistic role of CO₂ was realized through the gas phase reactions between volatile pyrolysates evolved from the thermolysis of SM and CO₂. In summary, CO₂ donates O, enhancing the generation of CO through homogeneous reactions. In parallel, this study confirmed that CO₂ suppress dehydrogenation. Therefore, the identified gas phase reactions between volatile pyrolysates and CO₂ led to the compositional modifications in the condensable pyrolysates. However, such mechanistic features arising from CO₂ only initiated at ≥520 °C. To expedite the reaction kinetics of the homogeneous reaction triggered by CO₂, steel slag (SS) was used as a catalyst. Hence, the reaction kinetics associated with the mechanistic role of CO₂ were substantially enhanced (up to 80%) when SS was used as a catalyst. Therefore, all experimental findings strongly suggest that CO₂ can be utilized as a raw material in a thermo-chemical process. More importantly, all observations suggest that CO₂ lopping can also be achieved in a thermo-chemical process. Lastly, this study shows that the high Cu content in SM was effectively immobilized through pyrolysis. Conclusively, this study experimentally proved that CO₂ could be promising for restricting the formation of toxic pollutant in the thermo-chemical treatment in that CO₂ offers an innovative and strategic means for controlling the ratio of C to H. Note that aromaticity and toxicity of chemical compounds are highly contingent on the ratio of C to H.

Biodiesel synthesis from fish waste via thermally-induced transesterification using clay as porous material

The valorization of organic waste through biodiesel synthesis was investigated to explore the concept of hazardous waste-to-energy. Fish waste (mackerel waste) was chosen as a case study because of the growing concern regarding the treatment of food waste, which is potentially hazardous to the environment. This study focused on the thermally-induced transesterification of fish waste for the production of biodiesel (i.e., fatty acid methyl esters (FAMEs)). This process requires a porous material that allows for the collision between reactants (fish waste and methanol) to increase inside its pores at high temperatures. Therefore, commercial clay (montmorillonite) was used as the porous material in this study. The optimal temperature for the thermally-induced transesterification of unpurified mackerel oil was 380 °C, and the FAME recovery reached up to ˜72 wt.%. This study also proved that thermal cracking of polyunsaturated FAME species was initiated at temperatures ≥390 °C, and that fish waste is a promising feedstock for biodiesel when it is produced via thermally-induced transesterification over clay as a porous material.

Chlamydomonas sp. as dynamic biorefinery feedstock for the production of methyl ester and ɛ-polylysine

An integrated production of methyl ester and ɛ-polylysine from Chlamydomonas sp. was studied using biorefinery approach. The harvesting efficiency of Chlamydomonas sp. was increased up to 92% by treatment with a flocculant FeCl₃ at 100 mg/L for 30 min. The DMC (dimethyl carbonate) mediated enzyme catalyzed in-situ transesterification of Chlamydomonas sp. yielded the maximum methyl ester of 92% under optimized conditions. The valued-added product ɛ-polylysine was produced from hydrolysate obtained from the spent biomass of Chlamydomonas sp. using Streptomyces sp. The key components of sugar and MgSO₄ used for ɛ-polysine production were optimized whereby the maximum ɛ-polylysine production was achieved at 50 g/L sugar and 0.3 g/L MgSO₄. The ɛ-polylysine production was further enhanced by supplementation of important amino acids (lysine and aspartate) and TCA cycle intermediates (citric acid and α-ketoglutaric acid). The maximum ɛ-polylysine production of 2.24 g/L was found with 4 mM citric acid supplementation after 110 h.

Biodiesel synthesis using chicken manure biochar and waste cooking oil

This study laid an emphasis on the possible employment of biochar generated from pyrolysis of chicken manure to establish a green platform for producing biodiesel. To this end, the pseudo-catalytic transesterification reaction using chicken manure biochar and waste cooking oil was investigated. Compared with a commercial porous material (SiO₂), chicken manure biochar generated from 350°C showed better performance, resulting in 95.6% of the FAME yield at 350°C. The Ca species in chicken manure biochar imparted strong catalytic capability by providing the basicity for transesterification. The identified catalytic effect also led to the thermal cracking of unsaturated FAMEs, which decreased the overall FAME yield. For example, 40-60% of converted FAMEs were thermally degraded. To avoid undesirable thermal cracking arising from the high content of the Ca species in chicken manure biochar, the fabrication of chicken manure biochar at temperatures ≥350°C was highly recommended.

Rapid biodiesel synthesis from waste pepper seeds without lipid isolation step

In situ transformation of lipid in waste pepper seeds into biodiesel (i.e., fatty acid methyl esters: FAMEs) via thermally-induced transmethylation on silica was mainly investigated in this study. This study reported that waste pepper seeds contained 26.9wt% of lipid and that 94.1% of the total lipid in waste pepper seeds could be converted into biodiesel without lipid extraction step for only ∼1min reaction time. This study also suggested that the optimal temperature for in situ transmethylation was identified as 390°C. Moreover, comparison of in situ process via the conventional transmethylation catalyzed by H₂SO₄ showed that the introduced biodiesel conversion in this study had a higher tolerance against impurities, thereby being technically feasible. The in situ biodiesel production from other oil-bearing food wastes can be studied.