Biogas production with select macro algae and nanoparticles added to anaerobic digester feedstock

Abstract

For qualitative and quantitative production of biogas, nanoparticles and use of macroalgae when added to AD feedstock at proper concentration, temperature and time of digestion can bring a revolution to meet the future needs of energy. The process of biofuel production can be altered by using various nanomaterials in various ways, such as by improving the stability of cellulose enzymes, enhancing the catalytic production of biohydrogen, and improving biological and chemical digestion. This influence of nanoparticles on the process is determined by their distinct catalytic activity based on structure, shape and size which is complementary to the relevant process. The addition of seaweed in the AD feedstock improves biogas output and digestate quality thus enhancing the economic viability with the simultaneous positive impact of reducing global warming.

Claims

1. A process for the production of biogas from biodegradable material which comprises the steps of: (a) adding the biodegradable material to the reactor; (b) adding manure to the feedstock; (c) adding a colloidal solution of surface-modified iron oxide nanoparticles and seaweed to the reactor; (d) providing anaerobic conditions; (e) carrying out the anaerobic digestion and collecting the biogas, liquid and solid wastes.

2. The process of claim 1 wherein the addition of NP results in greater optimization of the AD process and when combined with organic wastes in the AD feedstock will result in higher output of methane (CH.sub.4), Hydrogen (H.sub.2) and biogas.

3. The process of claim 1 wherein macroalgae in the form of specific seaweed species are added to the reactor to improve the nutrient content, biogas output and value of resultant digestate as a soil conditioner and fertilizer.

4. The process of claim 1 wherein the NP size (5 nm to 1,000 nm), composition (Fe.sub.3O.sub.4), at variable concentrations and AD process temperature (37° C.) and time (20 to 60 days) results in highly efficient biogas production.

5. The process of claim 1 wherein the mixture of seaweed species (Ascophyllum nodosum, Saccharina latissimi, Laminaria digitata, and Sargassum spp.) in wet or dry forms improves AD feedstock digestion, overall output of both the quantity and quality of biogas production and nutrient value of the resultant digestate for use as fertilizer.

6. The process of claim 1 wherein the addition of Ascophyllum nodosum in dry, powdered, wet or colloidal suspension to Nanoparticles of Fe.sub.3O.sub.4 from 5 nm to 1,000 nm in size will result in improved biogas production.

Description

SUMMARY OF THE PRESENT INVENTION

[0015] Accordingly, there has been a need for a novel improved anaerobic digester system and method for treating animal waste, manures, municipal wastewater or food wastes that may comprise the biogas system feedstock. As AD is essentially a mature industry and operation, production methods and system design are generally predictable, effective, durable, affordable for small scale systems, simple to operate, portable, and environmentally friendly. There is a further need for a novel improved anaerobic digester and method for primary waste treatment and biogas production for the small, medium, and large-scale farms to improve overall output and efficiency. The present invention fulfills these needs and provides other related advantages particularly high value fertilizer.

[0016] The specific shortcomings then where improvements are directed include incomplete digestion of the feedstock, resulting in poor biogas production, that limits the power production via electrical conversion, and providing less gas available for the production of heat. These shortcomings reduce the economic return from biogas plant operations and limit the sale of product outputs and subsequent revenue.

[0017] Other limitations that reduce operational efficiency of industrial scale plants include poor biodigestibility, unstable fermentation and low methane production. Attempts to resolve these essential problems with industrial scale biogas units generally fall into three basic approaches that include; [0018] 1. Pre-treatment of the input sludge including pre-heating, [0019] 2. Changes or adjustments in the feedstock mix that includes varying the proportions of manure, wastewater and other organic food wastes, [0020] 3. Changes in the digestive system including adjustments in the mix of temperature, AD time, and addition of supplements to feedstock.

[0021] This invention relates to this third option (3) of providing an optimized micro-environment that is produced by the addition of macroalgae and nano-particles to enable a more complete digestion of the feedstock organics based on improved physical, biological and chemical conditions that support and promote bacterial action. These optimal conditions are supplied by the invention mix of temperature, time of digestion, size of Fe.sub.3O.sub.4 particles (5 nm to 1,000 nm), of variable concentration and seaweed (macroalgae species) slurry or colloidal mix that consists of approximately between 2% and 20% of the total biogas feedstock by weight. Therefore:

[0022] In relation to microorganisms, there are two aspects to the impact of iron (Fe.sub.3O.sub.4 particles): (1) it serves as an essential trace element for anaerobe microbes and improves competition with sulphate reducing bacteria (SRB) leading to the growth and reproduction of methane producing microbes; (2) activities of the enzymes involved in methanogenesis and acidogenesis can be stimulated by iron due to its ability to improve basic elements in metallic-enzymes. The referenced analysis strongly suggests that both metabolically and technically, enhancement of AD by nano-ions is feasible and effective. Energy recovery through iron-based anaerobic digestion is a sustainable and promising strategy that covers many cross disciplinary fields. This technique can result in a novel industrial chain because it can interlink wastewater treatment, the steel industry, dairy and livestock agriculture and renewable energy generation.

[0023] Due to the presence of Fe.sub.3C and non-toxic Fe.sub.3C ions, methane production can be enhanced by a nano iron oxide (Fe.sub.3O.sub.4 NPs) and particularly nanoparticles of Fe.sub.3O.sub.4 from 5 nm to 1000 nm in size. When these materials were added to an anaerobic waste digester with variable concentrations at 37° C. for 20 to 60 days, there was an increase of 234% in methane production and 180% in biogas production, which could be considered the highest and most remarkable increase in biogas production using nanoparticles (Faisal, 2018).

[0024] By stimulating the bacterial growth, magnetite NPs (Fe.sub.3O.sub.4 NPs) can enhance methane production. The particle size, time and concentration determine whether there is enhancement, inhibition or adverse effects of energy conversion.