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Summary

An Italian Research Institute developed microbial mixed cultures able to effectively convert crude glycerol into hydrogen and ethanol, without the use of vitamins, mineral solutions or yeast extract. Energy conversion efficiency is 98%. The produced fuels (hydrogen and ethanol) reach both near-stoichiometric yields.
They are looking for partners able to test the technology at large plant scale.

Full description

The exponential production of biodiesel worldwide has led to a glycerol glut, and nowadays there is the clear need for a solution which might help valorise the glycerol surplus. The crude glycerol from biodiesel production is usually contaminated with water, methanol, soap, oil, and other compounds deriving from the transesterification process. These contaminants cause high purification costs, when converting crude glycerol by traditional chemistry methods, therefore the purification of glycerol (with a view to being sold) is not a viable option for the small or medium-sized biodiesel industry anymore. The use of low cost Biotechnologies to convert crude glycerol into higher-value products can therefore represent a promising route to achieve economic viability in the biofuels industry .
Our optimised process obtained a hydrogen production rate of almost 2.2L/L/day, with the degradation of 15.5g/L of glycerol within 48 hours (8g/L of ethanol). The scale-up allowed to reach about 3L/L/day of hydrogen (about 50% of biogas content) and the degradation of 20g/L of glycerol in around 50h. New experiments showed that ethanol concentration can easily be doubled and might be further increased.
The above-mentioned process has been set up in the Lab of Biomass and Bioenergy of an Italian government research Institute. The overall aim of the lab relies in the development of efficient biomass conversion processes, together with the development and demonstration of innovative technologies for the generation of biofuels. The activities are mainly focused on the selection and use of microbial pools for the production of II generation biofuels, applying the biorefinery concept and microbial ecology approach for sustainable energy production.
Main research activities are targeting:
" Biomass characterization and bioconversion
" Selection of functional consortia through bioaugmentation, acclimatization and enrichment
" Statistical optimization applied to biotechnology processes
" Development of two-stage bioconversion processes for hydrogen and methane production

According to the Biorefinery Concept, there are numerous possible applications for such a process. In fact it is possible to start with glycerol obtained through different processes (i.e. biodiesel from microalgae), and integrate it with other technologies, able to convert glycerol into energy and high-value products, such as: glycerol co-digestion, photofermentation by photoheterotrophic bacteria, coupling with Microbial Fuel Cells (MFC), as well as the coupling with methane production. The ethanol produced might be sold to the marked as bioethanol, re-used for the transesterification or even converted into hydrogen by steam reforming. Hydrogen might be used directly in fuel cells for electricity generation or used for hydrogenation of oils.

Innovative Aspects

The selection of a mixed culture directly on crude glycerol (instead of synthetic media) led to several advantages, in terms of reduced costs (no supplements, no need of sterile conditions, etc) and increased efficiency. In fact, selecting and isolating bacteria on synthetic medium (and pure glycerol) will lead to a decrease of yield when changing to biodiesel-derived crude glycerol. This is due to the fact that crude glycerol contains several contaminants (like methanol, salts, soaps, etc) that can inhibit bacterial growth. Therefore the selection and acclimation of a mixed culture directly on crude glycerol will help to better adapt the bacteria to the difficult conditions of the real substrate. Moreover, the use of a suitable mixed culture is particularly important when dealing with complex substrates, because syntrophic mechanisms and metabolic interactions among bacteria will help to circumvent inhibitory effects of refractory or toxic compounds. The efficiency of this cooperation allows to obtain comparable results, no matter if working with different kinds of crude glycerol, or even in non sterile conditions.
Based on preliminary evaluations, a 1000L pilot plant might produce around 500Kg ethanol/t of glycerol (with an estimated value of 350¬/t glycerol; based on prices of March 2011) and more than 250 m3 H2/t of glycerol (with an estimated value of 70¬/t glycerol; based on national subsidies of 0,28 cents/kWh).

Partner expertise sought:

The proposer is looking for industries/investors (in the Biofuel sector) interested in evaluating the offered technology on a large pilot plant scale, and eventually considering the possibility of a future cooperation and/or negotiation for licence agreement.