Slow Pyrolysis as a Method for the Destruction of Japanese Wireweed, Sargassum muticum

Abstract

Japanese wireweed, Sargassum muticum is an invasive species to Great Britain, which might be controlled by harvesting it for energy and chemicals. Pyrolysis is the thermal decomposition of the organic components of dry biomass by heating in the absence of air. The distribution of matter between solid, liquid and syngas depends on the biomass and the pyrolysis temperature and time. Slow pyrolysis with lower temperatures (~ 400⁰ C) tends to produce more solid char. Pyrolysis char can be an effective soil ameliorant, a sequestration agent due to its stability or burned as a fuel.The research attempts to answer the question: Could slow pyrolysis be an energy efficient means for the destruction of Japanese wireweed and produce a potential product, biochar? A simple test rig was developed to establish the yield of biochar, biocrude and syngas from the slow pyrolysis of Sargassum muticum. An energy balance was calculated using compositional data from the analysis of the seaweed feedstock, higher heating values (HHV) from bomb-calorimetry and literature values.The energy required to heat 1 kg of dry seaweed by 400⁰ C for slow pyrolysis was estimated at 0.5 MJ. The HHV of syngas and biocrude produced from the pyrolysis totalled 2.9 MJ. There is, therefore, sufficient energy in the biocrude and syngas fractions produced by the pyrolysis of seaweed to power the process and produce useful biochar, but insufficient energy for drying.

Golden Tides: Problem or Golden Opportunity? The Valorisation of Sargassum from Beach Inundations

“…Milledge and Harvey [34] found the C:N ratio of S. muticum to be 8. The C:N ratio of S. muticum can vary between 6 and 20 depending on location and season [32,51,52]. A high C:N ratio could be advantageous for the production of biofuels, but a low C:N ratio may be advantageous in the production of fertilisers and animal feeds.…”

“…Attempts to eradicate S. muticum have failed [28], and methods are being researched for its valorisation to encourage harvesting and control [29,30]. S. muticum has been suggested as a source of biochemicals, nutraceuticals, and pharmaceuticals [30,31]; a biorefinery feedstock [29]; and a biofuel feedstock [32][33][34]. The research and lessons learnt on S. muticum may be of value in seeking methods for the valorisation of the pelagic Sargassum species, S. natans and S. fluitans.…”

Changes in higher heating value and ash content of seaweed during ensiling

“…However, the losses of energy content during a year in ensiled storage are still considerably 362 below the energy required to dry seaweed which is equivalent to ~80% of the energy content 363 of the seaweed biomass (Milledge et al 2015). reasons for the differences observed in the friability of pellets formed from the ensiled 376 biomass of the two species of seaweed studied.…”

UK Macro-Algae Biofuels: A Strategic Management Review and Future Research Agenda

“…The paper "Macroalgae-Derived Biofuel: A Review of Methods of Energy Extraction from Seaweed Biomass" [44] provides an overview of the different methods of energy extraction making comparisons between them for readers who are interested in the technological aspects which are not the focus of this paper. Additionally, further research has increased our understanding of the various aspects of using seaweed as a potential biofuel examining issues such as ensilage, anaerobic digestion and slow pyrolysis [46][47][48], beach seaweed [49], dewatering treatments [44,50], potential products from seaweed [51], and a range of process hurdles [52].…”