Mobile Biomass Oil Refinery
Summary:
At the point of harvest, biomass might typically cost around $60 per metric ton. This equates to around $20/barrel equivalent or $0.50/gasoline gallon equivalent. Global total photosynthesis is around 130TW and global total fossil fuel use is around 16TW, so this is a resource that can scale to replace all fossil fuels. Oil refineries are typically over 90% efficient and cost around $4 to $12 per barrel, or $0.10 to $0.30 per gallon. The centrifuge reactor concept enables oil refineries to utilize biomass as a feedstock and be integrated into mobile harvesting machinery. This enables a near 3x reduction in the cost of common hydrocarbon fuels, disrupting the entire fossil fuel industry. It also enables distributed and democratized hydrocarbon fuel production, bypassing expensive, insecure, and monopolistic supply chains. Revenues that currently go to the fossil fuel industry will instead go to farming and forestry industries and resultant natural habitat and carbon removal benefits will avert a mass extinction and stop global warming.
The opportunity:
Forestry waste, agricultural waste, natural habitat waste, municipal waste including plastics, and effluent are all viable biomass feedstocks. The cost of biomass varies significantly by source and increased demand will result in higher costs. $60/tonne might be a reasonable average estimate, equating to around $20/barrel or $0.50/gallon equivalent - this is the arbitrage opportunity. Effluent and municipal waste often have a substantial negative cost. Natural habitat waste can also be negative due to a need to remove it to reduce wild fire risk. On the ground forestry slash often has near zero cost whereas forestry slash bundled and transported to the gate costs substantially more. At $60/tonne a 20 tonne truck payload is only worth $1,200, meaning that transporting biomass any significant distance by truck to a centralized processing facility is cost prohibitive. Collection and transport costs often dominate the cost of biomass, not the raw biomass cost. A mobile oil refinery that is located near the point of harvest, or ideally integrated directly into a harvesting machine, avoids these transport costs, dramatically reducing the cost of biomass and also greatly increasing the scale of the economically viable biomass resource. High value liquid hydrocarbon fuels are much more cost effective to transport than biomass and can be transported long distances.
Global photosynthesis is around 130TW with a little over half of this occurring on land. In comparison, global fossil fuel energy use is around 16TW. We also farm around half the world’s productive land, so agricultural waste alone could potentially be enough, although this is often more expensive due in part to alternate markets. Continuous selective partial harvest of natural habitat combined with forestry and agricultural waste can provide more than enough hydrocarbons to replace all fossil fuels, and at a substantially lower price. This also economically encourages the restoration of natural habitat and the aversion of a mass extinction, as hydrocarbon production allows natural habitat to generate substantial revenue - in excess of most low value farming. Farm gross incomes in the U.S. average around $1,700/hectare per year, but this is highly distorted by a small area of high value crops, the bulk of farmland generates far less revenue and outgoing expenses are often high. Biomass yields of around ten tonnes per hectare per year might be a reasonable average, and this might be achieved from natural habitat without substantial outgoing expenses. This could be highly profitable.
Ongoing selective partial harvesting of natural habitat can reduce invasive species and improve the recovery of native species, offsetting human impacts. It can also substantially reduce the risk of wildfires. A further advantage of the mobile oil refinery approach is that nutrients can be directly returned to the land, avoiding nutrient loss as is common in forestry and farming and thereby increasing sustainable yield. Only carbon and hydrogen are removed from the land, which are replenished via atmospheric carbon dioxide and rainwater. Additional fertilization can also be integrated into the biomass collection process, ideally using nutrients from wastewater treatment and/or seaweed from the ocean. This might increase natural habitat biological productivity by an average of around 30%. This would have a huge impact on biodiversity, hydrocarbon production, and atmospheric carbon removal. It would also greatly extend productive natural habitat into less optimal climates, mitigating desertification and increasing resilience to climate change. Even with ongoing income generating partial harvest and removal of hydrocarbons, managed natural habitat can support increased plant and animal populations and greater biodiversity.
We are currently in the middle of a mass extinction that we caused, primarily by replacing natural habitat with farmland. Catastrophic 73% decline in the average size of global wildlife populations in just 50 years reveals a ‘system in peril’. By averting a mass extinction we also stop global warming. We find that restoring 15% of converted lands in priority areas could avoid 60% of expected extinctions while sequestering 299 gigatonnes of CO2—30% of the total CO2 increase in the atmosphere, or 14% of total emissions, since the Industrial Revolution. Stopping the mass extinction is an even greater priority than stopping global warming. With help, it might take decades for the Earth to recover from global warming, but it can take millions of years to restore biodiversity after a mass extinction. Without nature, the need to stop global warming is also greatly reduced. The restoration of low value farmland to natural habitat does necessitate the diversification of food production. This can and will be accomplished by much more intensive robotic farming, desert farming with low-cost desalinated water, ocean seaweed farming, direct food synthesis, and so forth. These technologies are in active development and commercialization and should ultimately result in lower-cost, higher-quality, and more secure food supplies.
A solution:
The centrifuge reactor uses high pressure and temperature to replicate the process that naturally creates fossil fuels, but it does so in minutes instead of millions of years. It entails extreme process intensification and is able to produce more than its own weight in high quality liquid hydrocarbon fuels every hour. The centrifuge reactor also miniaturizes and integrates all the primary functions of an oil refinery and operates at comparable costs and efficiencies to an oil refinery (~$10/barrel and ~90% efficiency) while being able to use raw biomass as a feedstock. The centrifuge reactor uses high rotational speed to efficiently pressurize biomass to very high pressures. Heat recovery heat exchangers also increase the biomass temperature enabling hydrothermal liquefaction. Minimal external energy and biomass preprocessing is needed to achieve these high pressures and temperatures. This produces a mixture of water, salts, carbon solids, gases, and low quality oxygenated liquid hydrocarbons. Integrated steam reformation and hydrogenation is then used to remove oxygen and upgrade solid, liquid, and gaseous hydrocarbons into the high quality liquid hydrocarbon fuel of choice, such as gasoline, diesel, and jet fuel. Water, salts, and carbon dioxide are also produced, with the water and salt nutrients returned directly to the land. Everything produced is highly sterilized. The centrifuge reactor allows for active separation based on density, fractional distillation can also be integrated, and this allows for the exploitation of Le Chatelier’s principle so as to converge the overall chemical reaction on the desired hydrocarbon output. Undesired hydrocarbons are continuously recycled through the centrifuge reactor and this enables very high conversion efficiencies. Because all the primary oil refinery processes are integrated into one insulated pressure vessel thermal and pumping losses are minimal. Because of this the centrifuge reactor is capable of higher efficiencies than a conventional oil refinery, and it is far more compact. Due to the highly oxygenated low specific energy of biomass roughly half the carbon content ends up as carbon dioxide while the overall energy balance is relatively neutral. The centrifuge reactor requires little external energy to power it. Augmentation of the centrifuge reactor with external power can also convert the carbon dioxide into liquid hydrocarbons, roughly doubling yield, however this greatly increases complexity and will typically increase cost. Raw biomass at $60/metric ton roughly equates to $0.01/kWh of thermal energy, and few external energy sources are competitive with this or easy to integrate.
A woodchipper for preprocessing biomass to a granular size sufficient to fit through the intake might utilize around 1-2% of the biomass chemical energy content and might be needed for many applications. A woodchipper can be directly integrated into a biomass harvesting machine along with the centrifuge reactor, with hydrocarbon fuels produced by the centrifuge reactor used to power everything. The centrifuge reactor is also applicable to other high pressure and temperature reactions, for example, Haber Bosch for ammonia nitrate production (a primary fertilizer), can be directly integrated. This enables the centrifuge reactor harvesting machine to directly produce and distribute nitrate fertilizers as it operates. This could substantially reduce farming and forestry expenses while increasing yields, especially for lower value crops and in developing countries. The carbon dioxide produced by the centrifuge reactor is at supercritical pressures - it is liquid at ambient temperature. It can be collected, stored, and transported in high pressure cylinders should there be a commercially viable use for it. The centrifuge reactor can also be used to create methane, and in some ways this is a simpler process. The market value of methane is generally less than that of liquid hydrocarbons, and it would not have a significant cost advantage over natural gas, however it does burn more cleanly and there are markets that need it. It would be a renewable methane resource that would be a drop in replacement for natural gas. It would also be lower cost than liquefied natural gas for markets that lack low-cost natural gas resources. Advanced centrifuge reactors might eventually be used for the direct production of polymer precursors, solving the renewable plastic production problem. Many different reactions and processes can be integrated directly into the centrifuge reactor, including heat exchangers, catalysts, pressure changes, density separations, and even fluid logic. Different centrifuge reactors can also be operated in series, and not necessarily colocated, for example, a primary centrifuge reactor might be used to turn biomass into biocrude, for ease of transport, with additional centrifuge reactors for producing more refined products, which might be more centrally located. Ultimately, the centrifuge reactor is a new type of more efficient integrated high pressure and temperature chemical reactor that enables much greater process intensification. It can be used for a multitude of different chemical reactions.
The centrifuge reactor is a highly complicated piece of engineering entailing a many dimensional chemical reaction space contained within a high speed centrifuge operating at high temperature and pressure, which makes sensing and control difficult. It is not quick or easy for most engineers to understand, let alone optimize. As a general rule, integration increases performance and complexity, and this is the direction we need to move in. The centrifuge reactor almost needs AI to design, optimize, and operate it, fortunately this is becoming increasingly feasible. The engineering component challenges are all solvable and have been generally solved elsewhere, however solving them all at once on a highly constrained platform is challenging. The centrifuge reactor is subject to mass production and cost reduction curves such that the cost of this complexity is ultimately very low. Automotive manufacturing is indicative.
One of the design innovations is to use a thin wall metallic reactor vessel liner surrounded by fused quartz insulation that has very high compressive strength, which is wrapped with carbon fiber. This enables a very light-weight and low-cost reactor vessel which is capable of high speeds, pressures, and temperatures. Air cooling of the carbon shell is sufficient, avoiding the need for active liquid cooling. This even works if operating the centrifuge in a partial vacuum to reduce aerodynamic drag losses - heat transfer does not scale linearly with air density. The carbon fiber centrifuge reactor is around a tenth the weight and cost of what an inconel centrifuge reactor would be. One of the many engineering challenges are the high pressure and speed rotary seals needed for transferring multiple flows in and out of the centrifuge. There are many related technologies that solve similar sealing problems, including gas turbines, but this requires some engineering effort. All of the engineering challenges are solvable, but the amount of effort required varies.
The centrifuge reactor can scale from a few kilograms, for example, a home unit that processes household waste including garden waste, municipal waste, and effluent, to tens of metric tons. A likely practical size limit might be imposed by what can easily fit into a shipping container. There are two primary factors that favor the use of many small centrifuge reactors, they are the need to operate in a highly distributed manner close to the biomass source and the need for mass production and associated cost reduction curves. There is also a minimum size constraint set by labor costs if the system is human operated, for example if it is integrated into a biomass harvester system that has a human driver. Autonomous systems and automated stationary systems to which biomass is delivered are not constrained in this way. For example, robotic harvesting systems with integrated centrifuge reactors or centrifuge reactors that might be integrated into an effluent or municipal waste processing system. An advantage of larger centrifuge reactors is that the biomass feedstock can be of a much larger granular size - less chipping is required. However, larger centrifuge reactors also need larger biomass mass flow rates generally suggesting larger collection areas and higher biomass transport costs.
Status:
The centrifuge reactor is currently being prototyped and developed, slowly, on an unfunded basis. The carbon fiber pressure vessel has been constructed and has achieved high rotational speeds sufficient for high pressure without excessive vibration. The passive mechanical autobalancing system, where the movement of internal liquids actively balance the rotor, has been proven to work effectively. The next developmental step is to debug and incrementally improve the high speed and pressure stacked rotary seal system. After this the centrifuge reactor will be tested at pressure, and then at temperature, followed by the demonstration of hydrothermal liquefaction and the production of a biocrude. Some degree of steam reformation and hydrogenation may be achieved at this time, however for high performance operation a gas compressor will likely need to be integrated. This will pump light hydrogenating gases from the center to the tip, both greatly increasing the reaction rate and providing active control over the reaction speed. Catalysts may also be integrated to improve various reaction processes. Separation of carbon dioxide via fractional distillation may also be integrated, which with high speed and pressure rotary seals can potentially occur externally. This will greatly help drive the overall reaction towards upgraded low oxygen content fuels. More extensive design details will be posted when time allows.
With AI setting a new bar on scaling rates, and the need for hardware to keep up, we now need to go from idea to mass production in months not decades. Government and venture capital funding models for hardware are no longer timely or well aligned. Driven by the need to scale through companies that have already scaled, that already have the capital and manufacturing capacity, we are reverting to the technology licensing model. Which, for these general reasons, is used extensively in the pharmaceutical industry. The centrifuge reactor technology is available for open technology licensing and there is a patent on the technology. This is a highly complex engineering technology and it will require many teams of engineers to optimize it to its full potential - this is to be encouraged. The benefits exceed the costs by many many orders of magnitude and it is essential that these costs and benefits be shared.
