The Sustainable Hydrogen Economy: Methanol LOHC Gasification

The Sustainable Hydrogen Economy: Methanol LOHC Gasification

Abstract

There is an ever growing desire in our world today to store and transport hydrogen efficiently, sustainably and cost effectively. In the past few years, liquid organic hydrogen carriers (LOHC’s) have gained a lot of credence for their advancements in this space. The question we face now is, “how do we further advance these features while creating an affordable and environmentally sustainable solution that is accessible to all?” This proposal takes us through a self sustainable production plant that captures each of those aspects. It is carbon negative in practice, highly affordable and can even have net positive income with renewable energy credits and it is accessible to any human populated environment in the world. The LOHC’s features will have high hydrogen storage capacity, low hydrogen pressure and temperature for both the hydrogenation step and dehydrogenation step and low catalyst loading. This will be done through a matter of methods. These steps will involve sourcing of the material, the processes of the factory and the outputs this process will create.

Before we get into the material, let’s investigate the key player in this proposal - hydrogen. The hydrogen economy is one of growing importance. Its resulting impact could be a future of green energy, a crucial component of fragrances, pharmaceuticals and a wide variety of other industrial applications when carried and stored efficiently. It is a carbon free energy source, which is crucial in the carbon emissions avoidant culture the world is in today led by global environmental goals. Hydrogen is abundant and can be produced from renewable energy. It has high energy potential and potential for near-zero greenhouse gas emissions energy source. One of the major bottlenecks it has, however, is its storage and transportation. There are not efficient sustainable methods to store and transport this valuable element. That is where this proposal comes into play. It takes us through a circular sustainable model of transporting and storing hydrogen into much denser forms for beneficial release for its end use by means of methanol LOHC’s and a carbon negative gasification plant.

Material

The first step is gathering the biomass. There are five categories of biomass - wood, agricultural refuse such as husks and shells of rice and legumes, straw and manure, crops like corn or palm, industrial waste and sewage and refuse such as sawdust or carbon based byproducts of once living material. This alludes to every type of environment that these biomass converter plants can be installed. They can be urban and rural. They can be on farmland, near forests, in industrial centers, etc. Essentially there are no geographic limits to these centers. We can create LOHCs and their components everywhere.

The next step, after collecting any (or multiple) of the five categories of biomass that is most locally abundant, is gasification. Gasification is the process of heating biomass to temperatures 700-1000°C in a partial oxygen environment. This intense heat breaks biomass down into vapor, gas and char. Each of those has a use, which we will explore further below in Figure 1. Gas is blown through an extremely hot bed of fine char and during this gasification process, hydrocarbons are broken down into hydrogen and carbon monoxide. This produces our first set of hydrogen molecules to be entered into the LOHC’s further down the line of the process. Carbon monoxide (CO) can be used for a variety of applications. In medicine, CO applied in adequate doses to cells can reduce inflammation, defend from oxidative stress and prevent cell death. CO can be used as a catalytic converter in fuel cells. By oxidizing carbon monoxide, this CO can in theory be used as a catalyst for LOHC. This technology will need to be explored but the potential is there and that would make this system self containing and without any waste; all byproducts have a use and it becomes a green self-sustaining system.

The char is formed as a green energy source for the facility to run on - it keeps the lights on, it powers the chemical and physical reactions and it ensures the plant stays on. This allows even more of the solar energy to be sold, leading to direct profits on this system. Char can also be applied to farm fields as soil enhancing fertilizer. This exchange can be made to farmers who bring in their biomass to fuel the system. In exchange for their biomass, the next time they drop off the subsequent load of mass, they receive their respective portion of fertilizer. Biochar is recommended at no more than 10T per acre of land in production of field crops. If the application is home gardening, it is recommended to apply biochar to the top six inches of topsoil so that biochar makes up 5-10% of that soil. Biochar can be a source of revenue as well selling for up to $200/ton of material.

The vapor is condensed into water and this process is where one stage of water splitting occurs, resulting in our sought after hydrogen. These hydrogen molecules are split from oxygen (in H2O) through electrolysis and it is powered by the solar energy of the solar panels lining the roof and the biochar fuel being produced in the gasification chamber.

As the reverse of water splitting is the basis of hydrogen fuel cells, this will also be investigated as a method of clean energy. This reaction will be powered by the same renewable energy sources in this structure (solar and biochar). These hydrogen fuel cells can be sold for further income.

We will take this circular ecosystem one step further in the following models. We will have another water splitting step. This one will occur naturally through photosynthesis. We will install a greenhouse on the roof of the manufacturing plant, next to the solar panels (the solar panels will also line the outside walls of the building). Since gas and heat rise, the greenhouse will collect the byproduct carbon dioxide (CO2) from the gasification chamber. It will also collect water (H2O) from the vapor tube of the gasification chamber. The vapor will go through condensation and return water to its liquid state. These compounds (CO2 and H2O) along with sunlight shining through the windows make up the inputs for photosynthesis. The oxygen byproduct of O2 will be used during the oxidation process described below to transform carbon monoxide into a catalyst for LOHCs. This greenhouse is where photosynthetic water splitting (PWS) will occur. PWS occurs when light and catalysts (photosystem II (PS II) - an enzyme found in plants that facilitates photosynthesis - manganese, calcium and chlorine) are added to the photosynthetic process to generate hydrogen (protons), electrons and oxygen gas. As this is a naturally occurring process, the hydrogens will be isolated, captured and transported to the LOHC stage of the process.

The gasses include H2, CH4, nitrogen and CO, which we already discussed. The gasses that contain H will be split, similarly to the vapor, into hydrogen and their remaining components. The carbon-containing gasses will join the carbon monoxide and will be oxidized and converted into a catalyst for the LOHC hydrogen binding and release.

Methanol Creation

Methanol is a byproduct of the gasification system. Methanol has one of the largest volumetric storage densities ((3.3 kWh L−1) out of all LOHCs systems. It is also the most economical option. In this proposal, we will see how it fits into the circular sustainability to add even further benefit.

Transforming biomass into methanol involves multiple processes. We start with the collection of biomass to be funneled into the combustion chamber. The gasifier reaches elevated temperatures of >700 degrees celsius as heated by the steam pipe and The gasification process to create methanol goes through multiple processes. It goes through biomass

The heating stage occurs by elevating temperatures above 700 degrees celsius without combustion while controlling select amounts of oxygen in the environment. The gas travels through the cyclotron which allows for char separation and collection while the gas continues to conditioning and purification. This removes impurities such as tar and toxins. From here we produce a clean syngas which is then pressurized through compression followed by the methanol processing plant to obtain our methanol end product. Along the way, excess CO2 travels to the greenhouse for photosynthetic feeding and the vapor pipe both creates condensation for the greenhouse and also cycles back to heat the gasifier for additional heating to reduce energy input. The next stage is the pressurization to form a syngas - a mixture of carbon monoxide and hydrogen that gets sent to the methanol plant to make our methanol. This is where the syngas is reacted with a catalyst at elevated temperatures to form methanol.

Figure 1.

Methanol LOHC

Now that we have our methanol, we can combine it with our hydrogen and our catalyst (both produced as byproducts in the same facility) to get our green hydrogen carrying LOHC system.

LOHCs are a great class of hydrogen carrying due to their readily dehydrogenated principles at low temperature and high hydrogen capacity. Methanol LOHCs take these benefits a step further with exceptional volumetric storage density and in this model, eco-friendly sustainable methods of production. Methanol has a high energy output as well, which makes it suitable for efficient fuel cells (direct methanol fuel cells). This combination with hydrogen as one of the cleanest renewable energies there are (carbon free) creates an incredibly green energy source.

Figure 2. below Shows methanol’s dehydrogenation and steam reforming to isolate H2.

The carbon monoxide produced from methanol dehydrogenation will be captured and used for its intended purposes listed above - medicinal purposes and transformation into a catalytic converter. Any excess CO can be combined with O and sent to the greenhouse for green photosynthetic consumption. As discussed above, the oxidized CO is the primary catalyst for these reactions to continue the self sustainable low environmental and economical cost of this model.

This is the process that will create LOHC’s for all of its intended uses; whether it is fragrances, pharmaceuticals, fuel cells or other industrial applications, this processing system can cover them all. It does so sustainably, cost effectively (even profitably) and accessible by allowing essentially any environment to participate.

Conclusion

The key difference in this proposal is the circularity. It takes aspects that are currently occurring in our world today, and it applies them in combinations that are currently not occurring. That is where the innovation lies - it takes existing technology and combines it in nonexistent manners. This proposal creates a green solution to liquid organic hydrogen carriers (LOHCs) in an isolated carbon negative factory. It upcycles byproducts and waste streams to fuel other aspects of the manufacturing process. It transfers to renewable energy of both photovoltaic solar panels and biochar (another output of the gasification system). It allows revenue to be had through renewable energy credits. It uses naturally occurring and abundant free inputs and creates an innovative solution to hydrogen carriers that fuels itself, creates its own revenue and solves the proposals problem of sustainable synthesis for molecules to carry hydrogen in pharmaceuticals, heat-transfer fluids and fragrances, but it also opens up possibilities for a revolutionary production method of hydrogen fuel cells to being produced in a carbon negative manner.