Effect of Geographical Location on the Variation in Products Formed from the Hydrothermal Liquefaction of Ulva intestinalis

Abstract

Hydrothermal liquefaction (HTL) of macroalgae offers a promising route to advanced biofuel production, although the distinct biochemical compositions of different macroalgae species can lead to widely different product yields and compositions. On the basis of this, there is an implicit assumption that there exists a universal optimal feedstock species for a bioenergy-based biorefinery, which could be exploited across a wide region. However, no studies to date have examined the effect of this large geographical variation on a single macroalgae species for biofuel production. In this study, 24 samples of Ulva intestinalis were collected along 1200 km of Swedish coastline and assessed as a feedstock for HTL. Significant variation in composition was observed between samples from Baltic and Atlantic regions, but substantial variation also existed between sites within close proximity. This was reflected in the HTL biocrude oil yields, which varied between 9 and 20% (14–28% dry and ash-free basis) across the sample set. In a number of cases, greater variation was seen for adjacent sites than for sites at opposite ends of the sampling spectrum. Biocrude oil yields in this study also differed substantially from those previously obtained for U. intestinalis from the United Kingdom and Vietnam. Localized environmental conditions affected the HTL product composition significantly, in particular, the elemental distribution within the sample set. The variability observed in this study suggests that no single species will be dominant within a macroalgal biorefinery concept, but rather a species would need to be selected to match the needs of the exact local environment.

Effects of geographical location on potentially valuable components in Ulva intestinalis sampled along the Swedish coast

“…The samples were initially identified morphologically and were assessed as a feedstock for hydrothermal liquefaction (Raikova et al, 2020). However, recent studies have identified strong morphological plasticity within Ulva spp., as well as the occurrence of cryptic species within the genus (Steinhagen, Karez, & Weinberger, 2019).…”

“…Protein content was determined by analysing the nitrogen content on an elemental analyser (Carlo Erba Flash 2000 elemental analyser, at London Metropolitan University) and the nitrogen was converted to protein by a conversion factor of 4.73 (Biancarosa et al, 2017). Metals and some non-metal elements were analysed by inductively coupled plasma optical emission spectrometry (ICP-OES) after digestion in aqua regia as described (Raikova et al, 2020). ICP-OES was carried out externally by Yara UK Ltd using an Agilent 700 series inductively coupled plasma optical emission spectrometer.…”

Integration of algae‐based biofuel production with an oil refinery: Energy and carbon footprint assessment

“…Seasonal variations in growth and composition of Laminaria digitata and the implications for thermochemical and biochemical biofuel production routes were mapped by Adams et al 14,15 Their results show large variations in chemical composition throughout the year with July giving the best yields for such different processes as pyrolysis and fermentation to ethanol. Raikova et al 16 analysed the effect of geographical location on biocrude yields from macroalgae HTL, stating that significant variations in composition were observed between different regions (Baltic and Atlantic), but even between sites with close proximity. Localized conditions are considered to affect HTL product composition significantly.…”

Hydrothermal liquefaction of macroalgae for the production of renewable biofuels

“…Thus far, the most well researched macroalgae species have been from the genera Enteromorpha ( Ulva ) and Laminaria . Anastasakis and Ross described the HTL of three Laminaria types, as well as the brown macroalgae, Alaria esculenta , collected off the coast of Scotland, obtaining the highest yields of 13% bio‐crude for L. digitata and A. esculenta .…”

“…The compositions of the resulting bio‐crudes also displayed differences – H/C ratio varied from 1.04–1.28, and bio‐crude nitrogen ranged between 3.0–4.9%. A more recent study of geographical variation demonstrated that there is even a high degree of variability between bio‐crude yields from the same species of macroalgae collected at the same time from sites within relatively close proximity (on the km scale) …”