Onshore kelp anaerobic digestion process

Design of an onshore kelp anaerobic digestion process

Consumption of energy resources increasing constantly especially in industrialized countries which leads countries to concern about greenhouse gases because the energy sources we are using are non-sustainable and are the major reason for global warming. 97% of energy consumption is from non-renewable resources.

To cater the energy needs, sustainable use of resources is preferred in today’s world. Biomass can be an excellent source of renewable energy production.

Seaweed is one of them. Kelp is a type of seaweed that can be cultivated in nutrient-rich salty water. Kelp is an energy crop that is edible and according to studies, the use of these crops causes fewer carbon emissions hence making it a sustainable source of energy production

Onshore feasibility of kelp 

Kelp’s growth is based on meristem. Meristem is the place where blades and stipe meet. Its growth is limited by grazing. Its lifecycle consists of the diploid sporophyte and haploid gametophyte. The mature plant is formed after the diploid sporophyte. 

Harvesting of kelp requires a large amount of photosynthesis for maximum yield and it can easily be achieved onshore. Photosynthesis requires a large number of nutrients that can be easily available by onshore saline pools. Saline pools consist of a large number of salts and nutrients. Kelp is the seaweed that require plenty of salts and nutrients. Its growth majorly depends upon the temperature and light. 


The temperature in saline pools can be controlled in many ways and if we consider larger systems it may be impractical and uneconomical. Ambient temperature is not the optimal temperature but in some areas, the change in temperature is so small that the kelp adopts to this temperature and there is no need for controlling the temperature. Although temperature can be controlled, in some cases, it becomes unrealistic and uneconomical. 


Onshore saline pools, the growth, and reproduction of kelp depend on the light energy it receives. Light energy is the powerhouse of the system at the same time it cannot be controlled. That is why many experimental designs for the kelp growth rely on the artificial source of radiance. Hence more light energy causes more growth of kelp in onshore saline pools [4]. 

So, onshore saline pools have a higher capability for the generation of kelp. The only light is the limiting factor and due to this higher production is achieved. The density of biomass that is kelp has a higher effect on the production, so the biomass mustn’t attach to substrata. The dry part of the kelp contains low carbon content which can be an excellent source of sustainable energy needs. 

Figure 1 – Pictorial Diagram of saline pool harvesting


Anaerobic digestion is the conversion of organic matter into biogas mainly methane and carbon-di-oxide. It is the natural biochemical process that requires little or no oxygen. Anaerobic digestion also refers to the anaerobic decomposition usually on an industrial scale to decompose waste or specific substrate to produce biogas. Sustainable use of energy is the need of time and it can be achieved by producing less carbon foot and reducing greenhouse emission gases. Biofuels and biogas are the best Sustainable sources of energy that can be produced using seaweeds. 

Biogas from kelp can be obtained by kelp by decomposing it in an anaerobic digester. An amount of energy is released in a form of biomethane and some of it remains in the digester itself. The biogas obtained by the digestion process can be used for various purposes including powering heat electricity generators. The anaerobic digestion consists of the four main steps that are as follows 

  • Hydrolysis 
  • Acidogenesis 
  • Acetogenesis 
  • Methanogenesis 



Hydrolysis involves the breakdown of the non-soluble organic compounds to the soluble one using fermentative microorganisms. Pretreatment can be done to accelerate this phase. 


In this stage, the organic compounds degrade to form carbon dioxide, hydrogen gas, alcohol, and some organic acids. 


In this step, the fatty acids and alcohol convert into acetic acid, CO2 and H2 gas by the bacteria named as acetogenic bacteria. 


This is the last and the most important step in the whole AD process. In the process, the formation of biogas depends on the accumulation of VFAs, hydrogen pressure, buffering capacity CO2 concentration, H2 concentration. 

Following is the following diagram of the AD process 

Figure 2 – Flow diagram of AD process

Number of crops in high irradiation drought conditions 

Plants growth is highly dependent on light, water, and temperature. Unavailability of any of these may lead to a severe decline in plant growth. Any change in temperature due to physical damage or water shortage harms plant growth. Moreover, heat stress is the major contributor to a decline in plant growth.

Drought condition is caused when the water required for crops to grow is less or the rate of evapotranspiration is very high from their leaves. The severity of crop production in these circumstances is uncertain so exactly how many crops will survive these conditions is not sure. It depends upon the heat stress it has, the rainfall pattern, and moisture content it is holding. 




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