Process Engineering: From Beakers to Barrels
There has been a great deal of effort in recent years to develop algae growth technology; and for good reason, since some algae can produce biomass (and in particular lipids) at rates 10 times higher than terrestrial crops.
The algae value chain starts with sunlight, CO2 and water/nutrients, which are used by the algae to produce protein, starches and lipids that are then converted to various higher value consumer products. This process includes three distinct skill sets: biology, farming, and process engineering. While this article focuses on process engineering (biofuel and biobased chemicals production) a short description of the other two disciplines will help define the overall picture.
Biology: Strain selection and growth optimization is the first step in the algae value chain. Once the desired material to be produced is defined (lipids, protein, starch, or total biomass), an algae strain can be chosen or genetically modified to deliver the desired performance. Once the algae strain is chosen, the growth conditions must be optimized to meet the production goals. The right algae strain and growth conditions are essential to the success or failure of an algae project.
Farming: Cultivation and harvesting technologies for algae have taken many forms. Cultivation has been practiced in open ponds, photobioreactors, hybrid systems, and even in wastewater facilities. Harvesting (collecting the algae from the water) has been performed using belts, filters, centrifuges, gravity settlers, clarifiers using chemical additives and many others. Cultivation and harvesting technologies are currently technically feasible and algae biomass is now ready for further processing into higher value products.
Process Engineering: Extraction and processing of algae biomass yields algae oil, protein and starches. Algae biomass could also be converted directly into biocrude via pyrolysis. Conventional process engineering skills are used to develop the technologies required to perform extraction and processing of algae biomass. This is a critical step and work is ongoing to develop economically viable solutions.
Many traditional industries such as refining, petrochemical, oleochemical, and pulp and paper use the same proven technology frameworks that can be applied with some modifications and innovation to the extraction and processing of algae biomass. Emergent technology companies have used these established frameworks and developed effective and creative solutions. Established technologies like pyrolysis, hydrogenation, and solvent extraction have also been used to convert algae biomass into higher value products.
Algae biomass can be processed using pyrolysis to yield biocrude. The final objective is to create biocrude that can be fed directly into a refinery to make drop-in transportation fuels. There are a number of different ways to perform pyrolysis. Fast pyrolysis is the preferred route for land-based biomass, agricultural and forest byproducts essentially, since this biomass is relatively dry. Hydropyrolysis, or pyrolysis performed in water, may be more effective for algae biomass since it has high-water content, and water removal from algae biomass is very expensive.
Irrespective of the approach used, most of the algae biomass-derived biocrude is acidic and corrosive. This acidity must be removed to make the biocrude refinery ready. Hydrogenation has been used to deal with the acidity but this approach is burdened with high capital and operating costs. An alternative is the application of emergent technologies such as Enhanced Biofuels HS Reactor System, which can reduce this acidity in a cost-effective way via high efficient esterification.
Algae oil in the more popular algae processing scheme, extraction and processing are used to separate the algae oil, starches and proteins from algae biomass. In general terms, the process includes the following steps.
First algae biomass is dewatered, then it undergoes lysis (break-up of the cell wall to release the oil), and finally the oil is extracted by solvent or membrane technologies. The protein has uses in animal feed, and starches can be used in the production of ethanol. Algae oil can be used in the production of biodiesel, renewable diesel or aviation fuel, and lubricants and additives.
Fuel: Algae oil has been touted as a great feedstock for biodiesel, renewable diesel/jet due to its potential future abundance and molecular weight distribution, meaning smaller molecules similar to jet fuel. The high acidity of algae oil, however, could require extensive pretreatment steps and could be corrosive to the equipment and catalyst used in the processing of algae oil into fuel. A far more economic option is to minimize the acidity with the use of emergent technologies such as Enhanced Biofuels HS Reactor System, which would eliminate the need for extensive pretreatment steps and allow for the use of conventional metallurgy and catalyst.
Chemicals: Algae oil can also be used as feedstock for lubricity additives and some green lubricants because the algae oil has a very broad free fatty acid profile, which creates the potential for many different and likely higher value lubricity additives. Most lubricity additives are esters, so high efficiency esterification such as Enhanced Biofuels HS Reactor System should be the processing technology of choice to make these high-value products in a cost-effective manner.
The refineries and chemical plants of the future will look very similar to the refineries and chemical plants of today. They will use similar process engineering technology framework and infrastructure to create similar fuels and chemicals. Traditional and emerging technologies bring this processing experience and perspective to the algae biomass and algae oil processing industries.
Author: Roman Wolff
President, Enhanced Biofuels
The claims and statements made in this article belong exclusively to the author(s) and do not necessarily reflect the views of Algae Technology & Business or its advertisers. All questions pertaining to this article should be directed to the author(s).