D. Beneroso

Microwave pyrolysis of microalgae for high syngas production

The microwave induced pyrolysis of the microalgae Scenedesmus almeriensis and its extraction residue was carried out at 400 and 800°C. The results show that it is possible to obtain a gas fraction with a high content (c.a. 50vol.%) in H2 from both materials, regardless of the pyrolysis temperature. Furthermore, an outstanding syngas production and high gas yields were achieved. The maximum syngas concentration obtained was c.a. 94 vol.%, in the case of the pyrolysis of the residue at 800°C, indicating that the production of CO2 and light hydrocarbons was minimized. The same experiments were carried out in a conventional electric furnace in order to compare the products and yields obtained. It was found that microwave induced pyrolysis gives rise not only to higher gas yields but also to greater syngas and H2 production.

Microwave Pyrolysis of Organic Wastes for Syngas-Derived Biopolymers Production

Bioplastics production is a growing industry that offers an alternative to that of conventional fossil-derived plastics. Polyhydroxyalkanoates are biopolymers whose thermo-mechanical properties can be comparable to those of conventional plastics. Polyhydroxyalkanoates can be produced through the bacterial fermentation of carbon substrates, although to be commercially viable cheap renewable resources such as syngas (CO + H2 + CO2) from waste pyrolysis are required. Microwave pyrolysis has been demonstrated to have the potential of maximising both the gas production and syngas concentration. Hence it is an appropriate thermochemical route for further syngas fermentation. A combination of different factors, such as the type of waste, the moisture content, the pyrolysis temperature or the use of a microwave receptor makes microwave pyrolysis highly versatile, so that the syngas produced can be virtually tailored to the specific requirements of the bacteria.

Microwave-induced cracking of pyrolytic tars coupled to microwave pyrolysis for syngas production

Herein a new process is proposed to produce a syngas-rich gas fraction (>80vol% H2+CO) from biowaste based on microwave heating within two differentiated steps in order to avoid tars production. The first step consists of the microwave pyrolysis of biowaste induced by a char-based susceptor at 400-800°C; tars, char and syngas-rich gas fractions being produced. The tars are then fed into the second step where a portion of the char from the first step is used as a bed material in a 0.3:1wt% ratio. This bed is heated up by microwaves up to 800°C, allowing thermal cracking of tars and additional syngas (>90vol% H2+CO) being then produced. This new concept arises as an alternative technology to the gasification of biowastes for producing syngas with no need for catalysts or gasifying reagents to minimise tars production.

Syngas obtained by microwave pyrolysis of household wastes as feedstock for polyhydroxyalkanoate production in Rhodospirillum rubrum

The massive production of urban and agricultural wastes has promoted a clear need for alternative processes of disposal and waste management. The potential use of municipal solid wastes (MSW) as feedstock for the production of polyhydroxyalkanoates (PHA) by a process known as syngas fermentation is considered herein as an attractive bio‐economic strategy to reduce these wastes. In this work, we have evaluated the potential of Rhodospirillum rubrum as microbial cell factory for the synthesis of PHA from syngas produced by microwave pyrolysis of the MSW organic fraction from a European city (Seville). Growth rate, uptake rate, biomass yield and PHA production from syngas in R. rubrum have been analysed. The results revealed the strong robustness of this syngas fermentation where the purity of the syngas is not a critical constraint for PHA production. Microwave‐induced pyrolysis is a tangible alternative to standard pyrolysis, because it can reduce cost in terms of energy and time as well as increase syngas production, providing a satisfactory PHA yield.