The effect of mechanical pre-processing and different drying methodologies on bioethanol production using the brown macroalga Laminaria digitata (Hudson) JV Lamouroux

Abstract

Macroalgae are capable of generating more organic carbon per hectare than terrestrial plants without requiring land, fertiliser or fresh water to grow. In addition, they avoid the food versus fuel argument as they are not a major food source in Europe. In spite of these benefits, macroalgae are not yet fully exploited as a biomass source for bioenergy or platform chemical production in Europe, with one issue being the high harvesting and processing costs. This paper considers the impact of mechanical pre-processing of Laminaria digitata combined with different drying techniques and the effect of these on downstream processing to bioethanol. Results show that mechanically screw pressing macroalgae does enhance conversion to ethanol, but only when the material contains low levels of storage carbohydrates. This occurs in freezedried and air-dried samples. The addition of a press aid in the mechanical pre-processing step increases ethanol yields per gramme macroalgae, but due to the presence of the unutilised press aid in the fermentation, ethanol yields were lower overall. The two main findings from this work were (1) simple mechanical processing of L. digitata provides homogenisation and pumpability of macroalgae without negatively affecting subsequent microbial conversion to ethanol. (2) At higher carbohydrate concentrations, screw pressing confers no advantage in ethanol yields over strips of unprocessed kelp, making strips the more viable conversion option for low-input, large-scale processing.

Environmental hotspots of lactic acid production systems

“…Physical pretreatment, fermentation, and purification steps are assumed common for all three feedstock generations. For the third generation biomass, intensive air‐drying is chosen as a drying method due to current scalability issues of other methods, like freeze‐drying and mild‐air drying (Adams, Bleathman, Thomas, & Gallagher, ). Drying was included as a pretreatment method for three different reasons.…”

Effect of Chemical Pre-treatments on Bioethanol Production from Chlorella minutissima

“…Except Asia, algae avoid the food versus fuel argument since they are not a major food source. 6 Biomass production of algae is 5-10-times greater than that of land-based plants due to their more photosynthetic efficiency. 5 Algae grow rapidly and can be easily grown in various aquatic environments such as fresh water, saline water or municipal waste water.…”

A Review of Seaweed Pre-Treatment Methods for Enhanced Biofuel Production by Anaerobic Digestion or Fermentation

“…Unsuccessful ensilaging of Gracilaria vermiculophylla has been partly attributed to its high water content [58], which could be reduced by dewatering before ensilaging. Dewatering techniques include screw-pressing, using chemical additives, saline solutions or salting [75,83]. Screw-pressing itself has been found to increase ethanol yields of Laminaria digitata [83].…”

“…Dewatering techniques include screw-pressing, using chemical additives, saline solutions or salting [75,83]. Screw-pressing itself has been found to increase ethanol yields of Laminaria digitata [83]. However, these methods will also need to be selectively chosen for different types of seaweeds as it was found that red and brown seaweeds required different dewatering methods [57].…”

“…Chopping or milling of the biomass is commonly used to increase the surface area to volume ratio, in order to improve the hydrolysis of complex carbohydrates to sugars for fermentation or AD ( Figure 1A,B) [16,102]. However, the same milling techniques used for lignocellulosic terrestrial plants may not elicit the expected increase in surface area for seaweed [83]: milling of L. digitata, which has flat blades, did not significantly increase its surface area [103].…”