Nature’s Energy
How Do We Replace Oil and Gas?
At Metharc we have developed a method for the generation of hydrogen via biogas conversion within geothermal wellbores.
Global climate restrictions demand clean, carbon-free, energy sources. Geothermal energy meets these energy criteria, but the deep wells required to reach the high temperature geology are expensive to drill although they can be maintained over a typical 25-30 year lifespan. To improve the commerciality of geothermal energy, well costs need to be reduced and additional revenue streams are required.
The biogas-geothermal application of our Zero Carbon to Surface patent pending technology reduces the well cost and solves this revenue shortfall by supplementing geothermal energy with the production of hydrogen with simultaneously captured carbon downhole. To achieve this, biogas is injected from surface to a deep-set wellbore tool within the geothermal well. This environmentally-beneficial process future-proofs biogas reserves against climate regulations and increases the economic longevity of the existing geothermal and biogas infrastructures.
Replacing Oil and Gas with Biogas: Geo-Farming
Metharc enhances the geothermal energy sector within a biogas context, promoting the synergies between agriculture, biowaste and power generation within the circular economy. It enables the sustainable transition from a feedstock of natural gas to biogas for the production of hydrogen, playing an important role in waste management, while improving overall biowaste resource efficiency and geothermal economics by providing additional revenue streams.
Our technology enables the transition of biogas from being a hydrocarbon resource to becoming low-carbon hydrogen reserves, without the requirement to upgrade the biogas to biomethane. This will strengthen energy security, producing clean power from enhanced geothermal wells located close to biogas resources to optimise existing infrastructure. By decentralising hydrogen-electric power production, moving it closer to independent biogas producing sources, local energy and water requirements are better serviced with the option of feeding excess power into the national grid networks.
Biogas Resources
Biogas is produced from a variety of sources; agricultural biodigesters (crop and animal waste), landfill gas recovery systems (industry and domestic organic waste), and wastewater treatment plants (industry and domestic sewage). The biogas is produced when the organic matter (Biomass) is broken down by naturally occurring micro‑organisms via anaerobic digestion (in an oxygen-free environment). If the biogas is subsequently upgraded, by removing its CO2 content and concentrating its methane content to that comparable to natural gas, the biogas becomes known as Biomethane (also commonly referred to as Renewable Natural Gas).
The methane (CH4) content of biogas typically ranges from 45% to 75% by volume, with most of the remainder being carbon dioxide (CO2).
[Ref. : https://www.iea.org/reports/outlook-for-biogas-and-biomethane-prospects-for-organic-growth/an- introduction-to-biogas-and-biomethane]
The 2020 data from the International Energy Agency (IEA) shows the biogas production in Mtoe (million tonnes of oil equivalent) by region and by feedstock. As can be seen, there are currently significant biogas resources in Europe, shown by feedstock type. Huge potential also exists for the capture and conversion of biogas in the rest of the world.
As an example, pig farmers in the UK have found that the hydrogen generated from biogas is worth circa £300,000 per year on a 500-sow unit (£20 per finished pig). The hydrogen is used to power machinery, and using heat recovery, the harvested heat is used to evaporate water from slurry, producing saleable pelleted fertiliser, so there is no need for a slurry store. The Metharc biogas-geothermal process moves this biogas conversion downhole, and creates carbon capture as a free biproduct of the process.
[Ref.: https://ahdb.org.uk/knowledge-library/hydrogen-electrolysis]
[Ref.: IEA, Biogas production by region and by feedstock type, 2018, IEA, Paris]
[Ref.: IEA, Production potential for biogas or biomethane by feedstock source, 2018, IEA, Paris ]
Future Proofing Biogas Energy
Biogas is currently upgraded to biomethane, which produces CO2 when burned. Climate driven policies mandate reductions in the use of CO2 emitting fuels. This will inevitably lead to problems with the future use and disposal of biogas. Looking forward, this is a significant opportunity for the geothermal energy sector to improve their sustainability and commerciality by using the Metharc patent pending technology.
Note: Carbon Injection & Gasification Geothermal (CIGG) Carbon Capture & Storage (CCS)
Changing Habits
Our holistic approach couples both the biogas and geothermal sectors to generate hydrogen and CCS within the wellbore, creating more financially self-sustainable geothermal and biogas business models. This enables the accelerated expansion of both the biogas and geothermal energy sectors in tandem and creates improved commercial viability for any marginally economic geothermal developments.
Biogas plays an important part in waste management, improving overall resource efficiency, and yields energy security benefits. It can be developed at scale through integrated partnerships; with geothermal energy and district heating working closely with agriculture, landfill and biowaste to highlight their process overlaps and synergies.
The addition of CO2 within the power fluid allows for the rapid expansion of enhanced geothermal energy through a more sustainable business model, while capturing the biogas’ own carbon downhole within the geothermal reservoir. As all the carbon generated from methane reformation is simultaneously injected into the geological formations, climate advantages are immediate. Any additional, external, imported CO2 injection would provide more economic sustainability for those projects that pursue this as an additional revenue stream.
Through the transformation of a range of organic wastes into higher-value products, biogas fits well into the concept of the circular economy. In addition, by omitting the energy intensive and costly step of upgrading the biogas to biomethane, this enables operators of geothermal resources to generate and deliver hydrogen, power, water and district heating direct to customers at a lower overall cost.
Pollution free energy at a lower overall cost.
Pollution Free Growth
Usually, increasing agricultural productivity depends on adding something, such as fertilizer or water. A new Stanford University-led study reveals that removing one thing in particular – a common air pollutant – could lead to dramatic gains in crop yields.
Based on their observations, the researchers estimated that reducing NOx emissions by about half in each region would improve yields by about 25% for winter crops and 15% for summer crops in China, nearly 10% for both winter and summer crops in Western Europe.
[Ref. (June 2022): https://news.stanford.edu/press/view/43874]
Improving Food Production: Industrial Greenhouses & Geothermal
While food demand increases in line with a growing population, the land area and its’ availability to farm does not. To improve the productivity of farmland society needs to.
Increase Crop Productivity / Yields (Nutrient Availability)
- Nitrogen oxides (NOx) pollutants found in car exhaust and industrial emissions reduce crop yields. Conversely, low pollution can increase crop yields by between 10-25%.
[Ref. (June 2022): https://news.stanford.edu/press/view/43874]
Increase Resource Utilisation & Efficiency to Work the Land
- Utilisation of geothermal energy resources in synergy with agricultural waste will provide long term, stable energy pricing and improved farming business models, as the high variability of energy pricing in financial forecasting has a significant impact on farm profitability.
- Biogas-geothermal enables the utilisation of waste and recycling of water (for irrigation), provides heat and CO2 (for increased crop yields) from the enhanced geothermal systems, and enables both increased food production and efficient energy in synergy.
The Metharc biogas-geothermal application can provide both the heating and CO2 requirements for optimising greenhouse farming, together with a market for their waste treatment. Overall a circular green economy with a fossil-free reduced energy consumption.
Carbon Dioxide Supplementation
CO2 ppm – Although atmospheric and environmental conditions like light, water, nutrition, humidity and temperature may affect the rate of CO2 utilization, the amount of CO2 in the atmosphere has a greater influence. Generally, doubling ambient CO2 level (i.e. 700 to 800 parts per million) can make a significant and visible difference in plant yield. Plants with a C3 photosynthetic pathway (geranium, petunia, pansy, aster lily and most dicot species) have a 3-carbon compound as the first product in their photosynthetic pathway, thus are called C3 plants and are more responsive to higher CO2 concentration than plants having a C4 pathway (most of the grass species have a 4-carbon compound as the first product in their photosynthetic pathway, thus are called C4 plants). An increase in ambient CO2 to 800-1000 ppm can increase yield of C3 plants up to 40 to 100 percent and C4 plants by 10 to 25 percent while keeping other inputs at an optimum level. Plants show a positive response up to 700 to 1,800 parts per million, but higher levels of CO2 may cause plant damage (see Figure 1 below).
Temperature – Most biological processes increase with increasing temperature and this includes the rate of photosynthesis. But the optimum temperature for maximum photosynthesis depends on the availability of CO2. The higher the amount of available CO2, the higher the optimum temperature requirement of crops (see Figure 2 below).
Nutrients – A major effect of CO2 supplementation is the rapid growth of plants because of enhanced root and shoot growth. The enhanced root system allows greater uptake of nutrients from the soil. In general nutrient requirements increase with increasing levels of CO2.
[Ref. (March 2017) : https://extension.okstate.edu/fact-sheets/greenhouse-carbon-dioxide- supplementation.html]
Geothermal Heating of Greenhouses
Animal Breeding & Aquaculture
Alignment of Biogas Resources: Hydrogen with CCS
Through intelligent pairing, geothermal wells can be located close to biogas resources. This would provide not only enhanced power and district heating to consumers, but also CCS, hydrogen and water (for either irrigation or domestic use), with the utilisation of existing infrastructure for the minimisation of new-build requirements. These Enhanced Geothermal Systems (EGS) improve project economics by incorporating multiple revenues streams to put the Enhanced Geothermal Shot within reach.
The Enhanced Geothermal Shot
The Enhanced Geothermal Shot is a DOE research, development, and demonstration effort. Their goal is to reduce the cost of EGS by 90%, to $45 per megawatt-hour (MWh) by 2035.
There is enough technical EGS potential in the United States to meet the electricity needs of the entire world. Capturing even a small fraction of this resource via wide scale commercial deployment could affordably power more than 40 million American homes and businesses. Investments in EGS will also exponentially increase opportunities for geothermal heating and cooling solutions nationwide.
[Ref. Earth Energy Shots – Enhanced Geothermal (U.S. Department of Energy)]
The geographical overlapping of the biogas energy resources, and geothermal reservoirs provides an opportunity for their optimisation. The inherent synergy between them improves their sustainability and the security of our energy, water and food resources.
This updated 2023 map also shows the magnitude of biomethane produced, their relative energy values, (TJ/year) and the transmission systems involved.
[Ref. Courtesy of data and map owners, the Danish Energy Agency, Centre for Renewables, Biogas Plants]
Metharc anticipates that this infrastructure could be productively adapted and repurposed for hydrogen transportation as well as used in the CCS of biogas in geothermal wells for a truly circular economy.
The maps below from the Danish Energy Agency (DEA) (these maps are now obsolete) and the Geological Survey of Denmark and Greenland (GEUS) are good as an illustration of the immediate geographical benefits of overlapping locations of biomass/biogas production, biogas plants and the close approximation of potential geothermal reservoirs as CO2 disposal sites.
Less transportation of greenhouse gases results in lower transportation leakage emissions and a more efficient use of resources.
[Ref. Courtesy of Danish Energy Agency : https://ens.dk/en/our-responsibilities/bioenergy/biogas-denmark]
[Ref. Courtesy of Danish Energy Agency, Centre for Renewables, Biogas Production : https://ens.dk/sites/ens.dk/files/Bioenergi/biogas_kommune_2020_eng.pdf]
[Ref. Courtesy of Danish Energy Agency, Centre for Renewables, Biogas Plants: https://ens.dk/sites/ens.dk/files/Bioenergi/biogas_2020_06_eng.pdf]
[Ref. Courtesy of GEUS – The Geological Survey of Denmark and Greenland: https://dybgeotermi.geus.dk/wp-content/uploads/ROSA_WebGIS_portal_nr35_p23-26.pdf Vosgerau, H., Mathiesen, A., Andersen, M.S., Boldreel, L.O., Hjuler, M.L., Kamla, E., Kristensen, L., Pedersen, K.B., Pjetursson, B., & Nielsen, L.H. 2016. A WebGis portal for exploration of deep geothermal energy based on geological and geophysical data. Geological Survey of Denmark and Greenland Bulletin 35, 23–26.]
Geothermal Energy
Our patented process is easily adaptable for use within existing geothermal wells, improving infrastructure lifetime economics. It eliminates the need to permanently occupy vast areas of new land, forests, ecosystems (biodiversity) or farmland, impacting people’s livelihoods. Build costs are therefore lower than new industry, with less environmental impact.
Geothermal temperatures increase with depth (temperature gradient) and vary in different parts of the Earth, with a range from 10 to over 80ºC/km, and an average increase of about 30ºC/km. A high temperature gradient means that in order to obtain the same energy output, boreholes can be drilled shallower than those wells with lower temperature gradients. This has a direct effect on well costs. In addition, some thermal waters also have a natural methane content which can be utilised onsite. In general, reservoir thermal resources above 150˚C are used for electric power generation, while resources below 150˚C are usually used in direct-use projects for heating.
[Ref.: Geothermal Communities (a project of the CONCERTO initiative, co-funded by the European Commission within the FP7): https://geocom.geonardo.com/]
Temperature Profile versus Depth of the Earth’s Crust
[Ref.: https://geothermalcommunities.geonardo.com/elearning/repository]
Geothermal Potential
If the US could capture just 2% of the thermal energy available two to six miles beneath its surface, it could produce more than 2,000 times the nation’s total annual energy consumption. A noted MIT study in 2006 estimated that with a $1 billion investment over 15 years, enhanced geothermal plants could produce 100 gigawatts of new capacity on the grid by 2050, putting it into the same league as more popular renewable sources. (By comparison, about 135 gigawatts of solar capacity and 140 gigawatts of wind have been installed across the US.)
[Ref. MIT Technology Review (March 7, 2023) : https://www.technologyreview.com/2023/03/07/1069437/this-geothermal-startup-showed-its-wells-can-be- used-like-a-giant-underground-battery/]
Designing Power Systems for the Environment
Adopting a Zero Carbon to Surface philosophy for biogas injection improves commerciality through synergy with the geothermal energy resource that is neither variable nor intermittent. The resultant enhanced geothermal energy output will enable a more rapid transition to, and expansion of, a mixture of other green energy technologies.
The expansion of the both biogas and geothermal energy sectors would maintain continued mass employment from the technical overlap with the existing oil & gas industry (maintaining tax revenues) with technical knowledge and experience accelerating cost reductions. This maintains continuity in the use of the operational knowledge from many decades of well engineering and energy production experience.
With an expanded biogas-geothermal sector, the harmful recycling of captured atmospheric carbon (i.e., its re-generation and use as synfuels) would no longer be necessary, minimising this expensive, energy intensive and environmentally ‘neutral’ process.
It is far more beneficial to eliminate all carbon emissions at point-source, than extract them from the air after combustion, and avoids promoting climate solutions within a ‘post-burn’ narrative. This also avoids the climate damage done by these greenhouse gases while they are transitioning through the atmosphere prior to their, only partial, re-capture. The capture of carbon in geological reservoirs locks it in rock formations deep underground.
Geothermal Power Fluids: CO2 versus Water
The results indicate that the total exergy flow carried by CO2, in general, is 4.3 to 15.7 times higher than that for water, depending on the temperature and the pressure. It is also observed that, on a comparative analysis, more mechanical work can be converted from a reservoir with low temperature and low pressure.
Since the mass flowrate of the CO2 is about 5 times higher than that of water for the same driving force, the amount of useful mechanical work extracted from the heat content in a rock reservoir could be up to ten times more if CO2 instead of water is used as the heat extraction fluid.
[Ref.: The Exergy of Geothermal Fluids: CO2 versus Water. The National Energy Technology Laboratory, U.S. Department of Energy, GRC Transactions, Vol. 41, 2017: https://publications.mygeoenergynow.org/grc/1033857.pdf]
Biogas-Geothermal: Metharc’s CIGG Holistic Well Model
Conventional geothermal well designs can be adapted to include several additional revenue streams. Through our patented Zero Carbon to Surface process and philosophy, together with our patent pending technology, we can improve the overall profitability of standard geothermal wells.
What is CIGG?
Carbon Injection & Gasification Geothermal (CIGG) is a CO2 and biogas injection process, which gasifies (reforms) the biogas in the wellbore to generate hydrogen with simultaneous carbon capture within the geothermal reservoir. Through the adaptation and repurposing of mature industry technologies we have developed a patent pending process to enable a more sustainable geothermal energy sector.
Using our CIGG methodology, the methane (CH4) content of the biogas is converted to hydrogen within a deep-set wellbore tool. Together with any additional surface injected CO2, the generated CO2 high temperature waste stream from the wellbore tool is injected at-source, downhole. This high temperature waste stream eliminates any thermal depletion of the geothermal reservoir rock, and potentially creates a hotter-than-reservoir power fluid production (dependent on the through-reservoir distance to the geothermal production well). With the incorporation of carbon capture & storage (CCS), this injected carbon is captured and stored within the geothermal reservoir. A percentage of the total reservoir CO2 is recirculated in an adjacent geothermal production well system to be utilised to improve the overall energy efficiency and economics of the geothermal operations by enhancing the geothermal power fluid.
A typical geothermal well design for standard geothermal application is shown in the figure below. For comparison, the CIGG holistic philosophy is also shown, depicting multiple revenue streams. Horizontal wellbores within the geothermal reservoir distribute pressure across a large area, allowing greater volumes of flow. In addition, the heat generated by the wellbore tool within the CIGG process can be contained by tool placement within the horizontal section at a safe distance from the well’s intersection with the overlaying cap rock, ensuring the integrity of the well.
Biogas-Geothermal Technical Benefit
As all the generated CO2 from biogas reformation will be injected downhole, the process can enable the (optional) inclusion of extra, externally sourced and surface injected CO2. Direct use of produced CO2 in the power fluid in turbomachinery is also possible, and CO2 is a more effective fluid for heat extraction in geothermal applications while simultaneously allowing for the carbon capture (CCS) of some of the CO2.
In addition to the power fluid enhancement and CCS, this additional CO2 could also be used for either reservoir voidage replacement (i.e., re-pressurising a pressure depleted oil & gas reservoir) or as an Enhanced Oil Recovery (EOR) method to improve recoverable reserves towards yet more hydrogen generation and the longevity of the energy resource and its’ infrastructure.
This philosophy eliminates or minimises the need to occupy any new land, forests, ecosystems (biodiversity), farmland, or impact people’s livelihoods when utilising the existing energy infrastructure. Build costs and timelines are therefore lower than new industry, with less environmental impact.
Biogas-Geothermal Economic Benefits
The production of hydrogen not only generates additional revenue, but also offsets any carbon taxes by offsetting the equivalent carbon production. Combining the CCS injection of CO2 with hydrogen production also enables the possibility of additional external CO2 imported for capture & storage (CCS) at reduced cost. This additional revenue stream of carbon credits further reduces cost, and simultaneously, the carbon footprint. Producing energy with zero carbon will eliminates all carbon taxes, increasing profitability, however producing CO2 within the Power fluid improves energy efficiencies.
Generating hydrogen sales from the addition of biogas (CO2 & CH4) injection for capture & storage improves economics and reduces carbon footprint through combined synergy, accelerating the growth of geothermal energy projects and making marginal projects more commercial. Our concept utilises the existing energy infrastructure to improve their infrastructure lifetime economics (e.g., geothermal wells, declining oil & gas wells, pipelines, reservoirs), together with their conversion to geothermal operations.
Due to the lower surface tension at non-supercritical conditions, the use of CO2 within the power fluid also enables the extraction of heat from naturally existing, low permeability, geological formations. In addition, the hot exhaust (CO2 waste stream) injected from the Metharc tool enables lower natural temperature reservoirs at shallower depths to be used, which have better reservoir qualities (e.g., thickness, lateral extension, higher permeability and porosity). These shallower wells result in lower well costs. As these shallower formations have a lower natural temperature, they are normally excluded from standard water-based geothermal projects. The global accessibility to geothermal reservoirs will therefore expand significantly, due to the geothermal heat source no longer having to depend 100% on the natural reservoir temperature.
