Version: 2.0 (Redesigned)
Date: 17 June 2025
This document provides a comprehensive scientific, engineering, and financial feasibility analysis of synthesizing liquid petrol from atmospheric carbon dioxide, water, and renewable electricity—a process known as Power-to-Liquid (PtL). While each core stage of the process is scientifically sound, this report concludes that for an individual or small-scale operation, the project is practically unfeasible due to prohibitive costs and extreme, unmanageable safety risks.
The capital expenditure for the required specialized equipment is exceptionally high, estimated to be in the millions of Rands. The final fuel production cost is orders of magnitude higher than conventional petrol.
The process is fraught with severe hazards, including the generation and use of high-pressure, explosive hydrogen gas, the operation of high-temperature reactors, and the handling of corrosive chemicals. Managing these risks in a non-industrial setting is a potentially lethal undertaking.
The technology at the heart of this inquiry belongs to a class of synthetic hydrocarbons known as "e-fuels." These are advanced, carbon-neutral fuels produced by combining hydrogen (H₂) derived from renewable electricity with a source of captured carbon dioxide (CO₂). They are considered "drop-in" fuels, fully compatible with existing engines and infrastructure.
At its core, the PtL process is a method of energy storage. It is a net consumer of energy, with its viability predicated on abundant, low-cost renewable electricity. The overall "well-to-pump" efficiency is low; for every unit of electrical energy supplied, less than half is successfully stored as chemical energy in the final fuel product. [1, 2, 3, 4]
The capture process relies on a chemical reaction where CO₂ reacts with an alkaline solution of potassium hydroxide (KOH). The primary reaction is: [1, 5, 6]
2KOH(aq) + CO₂(g) → K₂CO₃(aq) + H₂O(l)
This reaction effectively scrubs the low concentration of CO₂ from the air and binds it in the liquid sorbent.
This module is an electrochemical system dedicated to producing green hydrogen feedstock via the electrolysis of water. For an application relying on intermittent solar power, a Proton Exchange Membrane (PEM) electrolyzer is technically superior due to its fast response time, though more expensive than alternatives. [9, 12, 13, 14]
The first step is the catalytic conversion of CO₂ and hydrogen into methanol.
CO₂(g) + 3H₂(g) ⇌ CH₃OH(g) + H₂O(g)
This requires a high-pressure, fixed-bed catalytic reactor. Unreacted gases must be separated and recycled back to the reactor inlet to achieve high efficiency, adding significant complexity.
The produced methanol is then converted into petrol-range hydrocarbons using a special zeolite catalyst called ZSM-5. A complex "hydrocarbon pool" mechanism occurs within the catalyst's pores, converting methanol to olefins, which then combine to form petrol components. The raw product requires fractional distillation to isolate the final, usable petrol fraction.
This section provides a realistic analysis of what a 'DIY' or small-scale build would entail, based on your specific questions. It is a thought experiment grounded in the research, intended to provide a clear-eyed view of the project's scope, not as an encouragement to proceed against the primary safety and economic recommendations.
Your proposal of covering a 300m² warehouse roof with solar panels is a solid starting point for generating the required power.
The panels are only one part of the equation. A 68.75 kW system requires a significant investment in inverters, mounting hardware, wiring, and most critically, a very large Battery Energy Storage System (BESS) to provide stable, 24/7 power to the reactors, which cannot be shut down intermittently. The BESS alone can easily cost as much or more than the panels.
A mini lathe and CNC machine are excellent for creating custom, non-pressurized components. This includes brackets for mounting sensors, custom enclosures for electronics, fittings for low-pressure tubing, and parts for the DAC unit's air contactor.
It is of critical, life-or-death importance that you do not attempt to fabricate any part of the high-pressure system yourself. This includes the main reactor vessels, high-pressure fittings, or any component that will contain hydrogen or CO₂ above a few bars of pressure. These parts must be professionally manufactured and certified from appropriate materials (like SS-316 or Hastelloy) to withstand the immense pressures and prevent catastrophic failure. A microscopic flaw created by a home machine could lead to an explosive rupture.
This summary outlines the most cost-effective, yet still formidable, pathway to building a system capable of producing approximately 3.8 litres of petrol per day. All costs are estimates in South African Rand (ZAR).
| Component | Cheapest Pathway Option | Estimated Minimum Cost (ZAR) |
|---|---|---|
| CO₂ Capture | DIY Open-Source DAC Unit | R65,000 - R85,000 |
| Water Purification | Reverse Osmosis + Deionization System | R20,000 - R50,000 |
| Hydrogen Generation | Alkaline Water Electrolyzer (AWE) | R40,000 - R60,000 |
| Gas Compression | Used/Surplus High-Pressure Compressors | R200,000 - R500,000+ |
| Methanol Synthesis | Used/Surplus High-Pressure Reactor | R300,000 - R900,000+ |
| Petrol Synthesis | Custom/Used Tubular Reactor | R100,000 - R300,000+ |
| Control System | PLC, Sensors, Professional Installation | R300,000 - R900,000+ |
| DIY Fabrication Tools | Mini Lathe & CNC Mill | R50,000 - R75,000 |
| TOTAL ESTIMATED MINIMUM | ~R1,075,000 - R2,870,000 |
Note: This total excludes the solar panels (~R150,000), battery system (~R200,000+), installation fees, and warehouse rental.
| Cost Component | Basis of Cost (per Litre) | Estimated Cost (ZAR) |
|---|---|---|
| Green Hydrogen Feedstock | ~0.71 kg H₂ per litre | ~R66.00 |
| DAC CO₂ Feedstock | ~2.64 kg CO₂ per litre | ~R20.00 |
| Electricity (Process) | ~6.6 kWh per litre | ~R24.00 |
| CAPEX Amortization | R2M CAPEX over 10 years | ~R145.00 |
| Maintenance & Consumables | 5% of CAPEX annually | ~R72.00 |
| TOTAL ESTIMATED COST PER LITRE | ~R327.00 |
Hydrogen is the primary safety concern. It is a colorless, odorless gas with an extremely wide flammability range in air (4% to 74%) and can be ignited by a tiny spark, including static electricity. Its flame is nearly invisible in daylight.
The process requires hydrogen to be compressed to pressures up to 80 bar (1160 PSI). A failure of a reactor, vessel, or fitting at this pressure would be catastrophic, resulting in an explosive release of flammable gas. [28, 1, 29, 30, 31]
Even with professionals hired for initial installation, the day-to-day operational risk remains extreme. The convergence of hazards—explosive gas, high pressure, high temperatures, corrosive chemicals—makes such a system fundamentally unsuitable for a non-industrial setting. Industrial facilities manage these risks through multiple, redundant layers of safety engineering, strict administrative controls, and highly trained personnel—resources that are unavailable to a private individual. Analyses by energy and safety institutions have concluded that hydrogen gas, particularly for combustion, does not belong in residential or lightly-controlled commercial settings due to the inherent risks of leakage and explosion.
Based on the overwhelming evidence of extreme complexity, prohibitive cost, and unmanageable safety hazards, it is the unequivocal expert opinion of this report that you should not, under any circumstances, attempt to build or operate this system.