Deep Green Path to Net Zero Carbon
Clean Fuels and Carbon Capture
The scientific community agrees that turning back the tide on climate change requires carbon dioxide emissions to be reduced to net-zero levels by 2050. It will take a portfolio of solutions to achieve net-zero, but I believe it is possible.
I will outline my portfolio of strategies in a brief overview. This portfolio requires new technologies, but all are in active development. I will dive into the details of each component in subsequent articles.
I start with the assumption that we can and should electrify light-duty transportation and space heating. This will eliminate most air pollution and create one of the biggest improvements in public health since the introduction of sewers, as well as some of the biggest reductions in carbon emissions.
We should expand wind and solar production as much as possible, but I am skeptical that we will hit high penetrations of wind and solar before land-use limitations cause growth to plateau. Any expansion of nuclear power is unknown since there are technical and economic barriers that need to be overcome. Some day nuclear power will be proven safe and cost-effective, but we don’t know if that day will come before 2050.
Coal and petroleum need to be left completely in the ground to have any hope of hitting net-zero, but we should expand the use of natural gas to balance wind and solar on the electric grid and to meet the needs of heavy transportation, industry, and the military. Over-reliance on electrical-only solutions like wind, solar, and nuclear requires a massive expansion of electrical transmission infrastructure while still not accounting for crucial energy demand sectors like the military.
Hybrid Methane-Electric Energy System
This clean energy model is built on a hybrid methane-electric system that captures carbon by three primary methods. First, biological sequestration of carbon by restoring ecosystems and regenerative agriculture which I suggest be funded through carbon pricing. Second, industrial carbon capture, utilization, and storage, with offshore hydrate formations providing a safe location for sequestering large volumes of CO2. Third, produce hydrogen from methane with a technical innovation that allows the carbon to be captured as carbon black, instead of conventional steam methane reforming that produces CO2.
The methane-electric energy system leverages existing natural gas infrastructure in a complementary marriage with the electrical infrastructure to provide a reliable and redundant system that meets the needs of all energy sectors while also delivering clean air, soil, and water.
All three legs I propose for carbon capture require extensive technical development. Biological sequestration requires a reliable system for monitoring, reporting, and verification (MRV) that does not exist today. Hydrate formations are a new frontier for both sourcing methane and sequestering carbon dioxide that is only just now being commercially explored. We also need a new method to produce hydrogen and carbon black from methane that can replace steam-methane reforming.
All the legs of this model are controversial and will invite criticism. Not all the methods are proven yet. But this model does provide a conceptual framework for hitting net-zero carbon emissions while maintaining an industrial civilization without the use of coal and petroleum.
Carbon Price and Ecosystem Renewal
CO2 and CH4 are the primary greenhouse gases and they are also part of the Earth’s biological processes. Nature wants to use these gasses to grow plants and wildlife, but unfortunately, humans have been destroying ecosystems for centuries and undermining the Earth’s capacity to absorb carbon. Half the battle in climate change is land use, we need to reform agriculture and our relationship to the land. By emphasizing the biological use of carbon we can turn nature back into the global carbon sink it is meant to be.
Biological sequestration is a complex subject with a great deal of scientific uncertainty over the details of carbon fluxes. The same patch of land will simultaneously absorb and release carbon dioxide over the course of its life cycle. But while there is uncertainty over the precise granular details of how carbon flows, the big picture is crystal clear. Hundreds of gigatons of soil and forest carbon have been lost due to human activities and reversing this trend will enable the Earth to absorb substantial amounts of carbon dioxide from the atmosphere while also improving fresh water and providing cooling shade. We just don’t know how large those final carbon counts will be.
Carbon pricing can be used to incentivize regenerative agriculture and ecosystem renewal. The “Carbon Deposit” is a pricing model where the funds raised from a fee on CO2 emissions is used to pay farmers and landowners for practices that sequester carbon in biology. The funds are paid out on a ton-for-ton basis and could create trillions of dollars in new revenues globally that would flow into organic agriculture and reforestation efforts.
$40/ton CO2 translates to nearly $150/ton for soil carbon, and one ton of soil carbon per hectare can be captured annually depending on the land type. Much work needs to be done to create a reliable MRV (monitoring, reporting, and verification) system for this to work and NORI is a startup business currently prototyping a solution.
Farmers who practice regenerative agriculture take care to improve soil health and they have been doing so for a long time. But there is no direct financial incentive to improve the land, farmers are only paid for the products they harvest and sell, not for the quality of their soil. The Carbon Deposit would provide a stream of income on the order of a cash crop that would reward farmers for improving their methods and soils.
Forests and wildlife habitat are under perennial pressure to be harvested, and their ecosystem services are not given a financial value in our economy. This is a market failure as ecosystems provide us freshwater, wildlife habitat, clean air, cool the planet, and improve human quality of life. The Carbon Deposit would fund the protection of wildlands by providing an income stream that incentivizes people to protect the land from resource extraction.
Ecosystems are networks of biological life and the carbon counts scale logarithmically as more wildlife returns. Rather than keeping nature behind fences in parks and preserves, we need to reestablish broad ecosystem corridors and networks that interconnect and reinforce one another on a global scale.
Changing land management and farming practices is as much about shifting cultural attitudes towards the land as it is about changing the finances. Financial incentives will signal to people the need to change their relationship to the land, but for good practices to stick our cultural values will need to reflect a genuine concern and passion for environmental stewardship.
CH4 and CO2 Work Together
A hybrid methane-electric energy system is built on existing natural gas infrastructure, covers all energy sectors, and meets the needs of heavy industry and the military. A hybrid methane-electric system provides redundancy and reliability to the electric grid and enables a web of reinforcing microgrids to emerge.
Leveraging existing natural gas infrastructure reduces the need to expand electrical transmission lines, though both systems need to be optimized and upgraded. CO2 pipeline infrastructure is needed as well for carbon capture, utilization, and storage.
Methane and carbon dioxide are complementary gasses that are used together in a variety of ways. Allam-cycle power plants are a new technology with integrated carbon capture. They make electricity from natural gas with no emissions to the air, all the CO2 goes into a pipeline. Allam cycle power plants have been proven successful and are now being built commercially.
CH4 and CO2 are combined to produce synthetic liquid fuels like methanol or DME and can be made into jet fuel. These methanol pathways enable us to make high-quality synthetic fuels that can have a high proportion of renewable and recycled content. There are other niche uses for captured CO2 as well, such as making concrete and plastics.
Methane is our most productive renewable fuel as well as our most abundant fossil fuel. We produce large volumes of renewable natural gas (RNG) today from biogas digesters, landfills, and sewage treatment that is injected into the natural gas pipelines. We can optimize our waste streams to eliminate landfills and process all of our carbon-based waste into RNG and synthetic fuels. Over time, we can maximize the renewable portion of our natural gas use.
Deep-Sea Hydrates
There are vast formations of methane hydrates on the deep ocean floor containing centuries of pure natural gas supply that can also accept endless volumes of CO2 in replacement. Methane hydrates are geological formations of ice called clathrates that form under conditions of cold temperatures and pressure. Most hydrates hold methane but they can also hold carbon dioxide or other gasses. Methane hydrates ring every continent at depths greater than 1500 ft (500 meters) where the continental slopes plunge into the deep ocean. It is estimated that there is twice as much methane hydrates as all the coal, oil, and conventional natural gas combined.
The hydrate formations are just beginning to be harvested commercially. Early work indicates that injected CO2 is needed to fill the pore spaces in the ice where the methane is removed. The CO2 hydrates keep the entire formations stable and intact. All of the drilling and refining work can be performed at sea with low environmental risk and at scales that can replace petroleum as the world’s primary energy source. The hydrate formations are a gift that offers an elegant zero-waste solution for producing natural gas while simultaneously storing CO2.
The public is not generally familiar with the methane hydrates, but the world’s oil majors see them as the new frontier. Sequestering CO2 in hydrates appears to be a huge improvement over the conventional method of sequestering CO2 in saline aquifers and oil wells because there is no limit to the storage capacity, the hydrates are stable on geological timeframes, and they are safely far away from people and no threat to wildlife.
Hydrogen and Carbon Black
Hydrogen has great potential to fill a role as a form of zero-carbon stored energy. The challenge to using hydrogen lies in identifying the optimal resources and distribution methods. Most hydrogen today is produced from fossil fuels using a method called steam-methane reforming that produces large amounts of CO2 as a waste product.
The environmental community generally promotes the electrolysis of water using renewable electricity to make hydrogen, but this process suffers from poor economics and thermodynamics when electricity is used to make hydrogen which is then converted back into electricity.
A simple solution to producing hydrogen is to innovate an alternative method to steam-methane reforming that produces solid carbon black as a byproduct instead of CO2. CH4 is the most hydrogen-rich molecule found in nature and methane is already our primary source of industrial hydrogen. It is inherently less energy-intensive to separate the hydrogen from a CH4 molecule than from an H2O molecule.
Carbon black is elemental carbon in a solid form, typically as a fine black powder. We see carbon black in the soot residue from smoke and it is widely used in manufacturing for everything from inks to carbon fibers.
It takes heat to separate methane into hydrogen and carbon black and numerous processes exist for it. One promising method currently being researched bubbles methane up through a column of molten metals. The carbon separates and floats on the surface as carbon black while the pure hydrogen floats out the top and is collected. A method such as this is needed and will transform the CO2 waste product from hydrogen production into a commodity material.
Hydrogen is also a difficult and dangerous molecule to work with and expanded hydrogen pipelines present serious risks to public safety. Hydrogen is expensive to work with because it is tiny, leaks easily, does not readily compress, is highly reactive with common materials, and is extremely volatile and flammable. A small network of hydrogen pipelines currently exists that links petrochemical refineries along the Gulf coast. These pipelines are far more expensive than natural gas pipelines because they require special materials and extensive monitoring for safety.
It makes little sense to build a new network of hydrogen pipelines when we already have natural gas pipelines to use for hydrogen distribution. Hydrogen can be produced regionally from natural gas and bottled into appropriate containers for retail distribution.
Hydrogen fuel cells could play an important role as electric generators and electric vehicle range extenders. Hydrogen fuel cells can be used to charge batteries independent of renewable sources or grid power. They could contribute to a network of interdependent micro-grids and also upgrade battery-only electric vehicles.
Conclusion
This article is an introductory overview. I will dive into the technical details, opportunities, limitations, and controversies in subsequent articles. In summary, a methane-electric energy system can achieve net-zero carbon emissions by relying on natural gas to replace both coal and petroleum. Carbon is captured through biological and industrial means as well as hydrogen production. This system covers all energy sectors, is reliable and redundant, and provides liquid fuels with high ratios of renewable content.