MicroalgaE biomass from phototrophic-heterotrophic cultivation using olive oil Wastewaters

PROJECT DESCRIPTION

BACKGROUND

The EU produces about 70% of the world's olive oil (some 4.5 million tonnes per year). Spain, Italy and Greece are the three main producers. The manufacturing process involves separating the oil from the solid fraction (pomace) and waste vegetation waters. Three tonnes of wastewater is produced for every tonne of olive oil. As well as a high organic load (chemical oxygen demand of 40 000 to 190 000 mg/litre), this waste contains phenols and polyphenols, which have anti-microbial and phytotoxic effects, preventing its use as a fertiliser.

Wastewaters from olive oil production typically cannot be treated in conventional biological depuration plants, due to the toxic effect of antioxidants on active sludge. Thus, in Italy it is typically directly applied on soil, left to evaporate and become sludge (which must be disposed of), or sent to composting plants.

OBJECTIVES

MEWLIFE seeks to turn waste vegetation waters from olive oil production into a resource. It will pilot the use of pre-concentrated wastewaters as a carbon source for growing microalgae by means of an integrated phototrophic and heterotrophic cultivation system. It is hoped that this will cut the cost of large-scale microalgae cultivation by demonstrating the feasibility of an alternative to expensive photobioreactors. This would also have a positive impact on land use.

The dried microalgal biomass will be assessed to see whether it can be used in neutraceuticals (products derived from food sources that can provide extra health benefits). This will involve evaluating the impact of cultivation in an antioxidant-rich medium on potential health benefits. The MEWLIFE team will also test samples of fractions extracted from the biomass to assess its suistability for producing bio-plastics. Substituting microalgae for crops currently used to make biopolymers could have positive effects on food security.

By reusing wastewater, the project will contribute to the delivery of the EU's circular economy action plan. It will also directly support the implementation of the Waste Framework Directive and Water Framework Directive.

Expected results:

Prototype unit for dark fermentation (reactor volume: 6 m3);

Prototype unit for algal biomass harvesting, dewatering and packaging (estimated capacity 3 kg/day);

Treatment of some 40 m3 of vegetation waters from the olive oil sector to produce an organic concentrate (4 m3) which will be used in the dark fermentation of microalgae, and depurated water to be discharged in public sewer networks;

Production and packaging of 1 tonne of dried biomass;

Production of at least 2 kg of starch from lab scale equipment using a representative sample of algal biomass produced within the pilot activity; the starch will be characterised and used to produce bio-plastic;

Determination of the nutraceutical characteristics of representative sub-samples of algal biomass;

Improvement in algae cultivation: (i) Produced algal biomass: >10 kg/batch; (ii) Energy consumption: >70% saving with respect to prototrophic systems for the same amount of algal biomass; (iii) Nutrients consumption: >10% saving with respect to prototrophic systems for the same amount of algal biomass; (iv) Land use: >90% reduction with respect to pure phototrophic systems for the same amount of algal biomass.