THERMAL, ALKALI AND THERMO-ALKALI PRETREATMENTS APPLIED ON MONOSPECIFIC MICROALGAL BIOMASS TO IMPROVE ANAEROBIC BIOGAS PRODUCTION

In last years microalgae biomass has been used for several scopes. One of them is to investigate their use as energy products. In this work microalgae were studied for anaerobic digestion use, but, to do so with a positive cost/revenue ratio, the cell walls must be efficiently removed before that the anaerobic digestion process takes place. This is the only way to make available the organic matter for the microbial activity and consequently enhance quantity and quality of produced biogas. In this study were used Scendesmus obliquus strain treated with thermal, alkali and alkali-thermal pre-treatments. Samples of microalgae biomass were collected and subjected to a first pre-treatments test at 120°C (autoclave) for one hour and half. The second test was performed with an alkali pre-treatments using NaOH with a dosage range from 4 to 20% of the selected TS matrix (2, 5, 10% by weight). The last test was conducted using a hybrid pre-treatment (alkali – thermal), with the same dosage of NaOH and thermal exposition described above. Both tests with the use of NaOH showed a better efficiency in releasing intracellular organic matter and breaking polymeric bridges. Then biogas potential tests were performed under batch mesophilic conditions after each pre-treatment to evaluate possible enhancement in biogas production and quality.