How to turn waste gas CO into treasure? Photovoltaic wind power + green hydrogen gives the answer to carbon neutrality

I. Dilemma of traditional CO governance and breakthrough opportunities for renewable energy
(I) The dual nature of industrial CO emissions
As a typical byproduct of the steel, coking, chemical and other industries, CO emissions exceed 300 million tons per year worldwide, with two major characteristics:
Pollution threat: Excessive concentration in low altitudes can cause hypoxia and poisoning in the human body, and high-altitude accumulation has a greenhouse effect potential 11 times that of CO₂, exacerbating climate warming;
Resource value: Its molecular carbon content is 42.9%, and 1 ton of CO can theoretically be converted into 0.75 tons of methane, with a calorific value equivalent to 0.5 tons of raw coal.
Traditional treatment methods such as incineration (converted into CO₂) or adsorption (cost 200-300 yuan/ton) either transfer pollution or have poor economic performance. The explosive growth of photovoltaic and wind power (global new installed capacity will exceed 300GW in 2023) has brought about a key turning point - its surplus electricity drives water electrolysis to produce hydrogen, providing a zero-carbon hydrogen source for CO conversion and promoting the transformation from "end-of-pipe governance" to "value creation."
(II) Catalytic methanation: the "carbon-hydrogen marriage" of CO and green hydrogen
The core reaction is based on the Sabatier principle (CO + 3H₂ → CH₄ + H₂O), and is mediated by catalysts such as Ni-CeO₂, achieving two major technical advantages:
Mild conditions: At 200-300℃ and 1-3MPa, the CO conversion rate exceeds 92%, and the methane selectivity reaches 95%, which reduces the energy consumption by 40% compared with the traditional fossil energy hydrogen production path;
Storage and transportation friendly: The liquid density of methane is 423kg/m³ (2.5 times that of hydrogen), and it can be directly transported using the global 4 million kilometers of natural gas pipeline network, avoiding the safety cost of high-pressure storage and transportation of hydrogen.
II. Three major synergistic scenarios of photovoltaic wind power and CO conversion
(I) Renewable energy consumption: a new energy storage solution to solve the "power abandonment dilemma"
In the northwest wind power base and the photovoltaic-rich area in North China, the power abandonment rate has been higher than 15% for a long time, and the "wind and solar power generation - water electrolysis - methanation" system has become the key to breaking the dilemma:
Power time and space transfer: low-peak wind power at night and excess photovoltaic power at noon are converted into hydrogen, which then reacts with industrial CO to generate methane. Taking a 50MW photovoltaic power station as an example, the annual consumption of 15 million kWh of abandoned power can produce 300 tons of methane, which can meet the daily gas consumption of 300,000 households;
Inter-seasonal energy storage: converting surplus power in summer into methane storage, and using it for heating or power generation in winter, solving the contradiction between "output fluctuation" and "energy rigidity" of new energy, and the energy storage efficiency reaches 65% (better than 55% of lithium batteries).
(II) Industrial emission reduction and energy self-sufficiency: Park-level multi-energy complementary practice
In steel and coal chemical parks, this technology achieves the dual goals of "emission reduction + efficiency improvement":
Waste gas resource utilization: After the coke oven gas (containing 10-20% CO) of the coking plant is captured, it reacts with the green hydrogen produced by photovoltaic electrolysis of water, and the generated methane is reused for blast furnace heating, reducing raw coal consumption by 15% and CO emissions by 80%;
Energy closed loop: synthetic methane is incorporated into the park energy network, 1m³ methane can generate 3.6kWh of electricity and 12MJ of heat, and the comprehensive energy efficiency ratio of a demonstration project reaches 85%, which is 20% higher than the traditional coal-fired system.
(III) Implementation of negative carbon technology: from industrial emission reduction to atmospheric carbon capture
Combined with the CCUS (carbon capture, utilization and storage) concept, this technology extends to a wider range of scenarios:
Deep decarbonization of heavy industry: After the CO (concentration 5-8%) in the tail gas of the sintering machine of the steel plant is converted, each ton of CO processed can reduce 1.7 tons of CO₂ emissions (compared with the incineration method), and the annual production of 100,000 tons of synthetic methane is equivalent to 270,000 tons of fixed CO₂;
Prospects for atmospheric carbon capture: In the future, if coupled with direct air capture (DAC) technology, CO extracted from the atmosphere will react with green hydrogen to achieve "negative carbon emissions" and build an "artificial carbon cycle" ecosystem.
III. Technological breakthroughs and global implementation cases
(I) Catalyst innovation: from "high temperature and low efficiency" to "low temperature and anti-toxicity"
Early Ni/Al₂O₃ catalysts need to operate above 350℃ and are susceptible to sulfur poisoning. Nanotechnology promotes two major breakthroughs:
Core-shell structure design: Ni-CeO₂ nano core-shell catalyst reduces the active temperature to 250℃, CeO₂ shell captures H₂S to generate inert sulfate, and the anti-sulfur performance is improved by 3 times;
Bimetallic synergy: Co-Ni alloy catalyst increases the methane generation rate by 50% through electronic structure regulation, and the processing capacity of a single reactor increases from 5000m³/h to 7500m³/h.
(II) Large-scale practice: from laboratory to commercial operation
1. German Power-to-Gas benchmark project
The Hamburg WindGas project integrates 5MW wind power, produces 120 tons of hydrogen per year by electrolyzing water, and reacts with 400 tons of CO from surrounding chemical plants to generate methane, which is integrated into the natural gas pipeline network to meet the gas needs of 3,000 households. The CO conversion rate has been stable at more than 92% in 7 years of operation, becoming a European renewable gas demonstration template.
2. Pilot project of green electricity conversion of coal chemical industry in Northwest China

A coal chemical park in Shaanxi Province built a methanogenization unit with an annual processing capacity of 50,000 tons of CO and a supporting 100MW photovoltaic power station:

Economic feasibility: The price of synthetic methane is 2.8 yuan/m³, with an annual income of more than 20 million yuan and an investment payback period of 5 years;

Environmental benefits: Annual reduction of CO emissions by 50,000 tons, equivalent to the carbon sink capacity of planting 270,000 fir trees.

IV. Challenges and future: from technical breakthroughs to market explosion

(I) Scale bottleneck and breakthrough path

Cost barrier: The current cost of synthetic methane is about 3.5 yuan/m³ (higher than 2.5 yuan/m³ of natural gas), mainly because hydrogen production by electrolysis of water accounts for 60% of the cost. With the cost of photovoltaic and wind power falling to less than 0.2 yuan per kilowatt-hour (estimated in 2025), coupled with the large-scale production of electrolyzers (cost reduction of 40%), it is expected to achieve cost parity in 2025.
Catalyst life: Dust and heavy metals in industrial waste gas can easily lead to catalyst deactivation. It is necessary to develop porous ceramic carriers or self-cleaning coatings to extend the replacement cycle from 1 year to more than 3 years.
(II) Dual opportunities of policy and market
Carbon trading value-added: Synthetic methane can apply for CCER (National Certified Voluntary Emission Reduction). Calculated at 50 yuan/ton CO₂, an annual treatment of 100,000 tons of CO projects can obtain an additional income of 5 million yuan;
Global market expansion: The EU "Renewable Methane Directive" requires that renewable gas account for 20% of the transportation sector in 2030, which is expected to give rise to a market of hundreds of billions of yuan. China's "14th Five-Year Plan" CCUS plan also opens up new space for industrial emission reduction for this technology.
Conclusion

When the sunlight captured by photovoltaic panels and the wind energy harvested by wind turbines meet the CO waste gas from industrial chimneys, a "midas touch" about carbon neutrality is taking place. From waste gas treatment to energy production, from cost center to value hub, this transformation not only reshapes the logic of industrial waste treatment, but also builds a new paradigm for renewable energy storage and utilization. With the iteration of catalyst technology and the release of policy dividends, "green electricity hydrogen production + CO methanation" is expected to become another "zero-carbon pillar" after photovoltaic and wind power, contributing innovative solutions to "waste gas resource utilization" for the global carbon neutrality goal.

author：Hazel
date:2025-05-28