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How “clean” hydrogen fuel can pollute the atmosphere more than gas and coal

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According to scientists, one of the primary strategies for resolving the climate crisis – the use of so-called blue hydrogen – may not be as environmentally friendly as originally believed.

The carbon footprint of this apparently “green” energy source could be 20% more than that of natural gas or coal combustion.

Previously, experts and even governments thought that blue hydrogen holds the key to resolving the world’s energy and environmental crises. However, research published in the journal Energy Science and Engineering shows that it is not as environmentally friendly as stated.

Hydrogen as an energy source is, in fact, an environmentally friendly option. However, hydrogen must still be created in order to accomplish this.

Blue hydrogen synthesis generates significant volumes of carbon dioxide and methane. The technologies used to capture them are not flawless, and typically miss between 10% and 15% of the CO2 produced.

According to a new investigation, blue hydrogen has a carbon footprint that is 20% greater than natural gas combustion directly. Additionally, it emits 60% more emissions than diesel.

The study was released two days after the United States Senate passed the $1 trillion Infrastructure and Jobs Investment Act, which included a $8 billion investment in hydrogen energy. Simultaneously, the governments of the United Kingdom, Canada, the European Union, China, and a number of other countries are gradually moving toward hydrogen as a clean fuel source. Scientists, on the other hand, believe that politicians do not completely comprehend all of the repercussions.

“Political forces may still be lagging behind science. Even progressive legislators may be unaware of the issues on which they are voting. Blue hydrogen seems good, modern, and like the way forward for our energy future. However, “Robert Howarth, co-author of the study, stated.

The great majority (96 percent) of hydrogen is created from fossil fuels, primarily by natural gas steam methane reforming (SMR), but also through coal gasification.
Blue hydrogen is used to capture some of the carbon dioxide produced during the SMR process. Another variation on the blue-hydrogen process removes additional carbon dioxide from the flue gases produced by natural gas combustion to generate the heat and high pressure required to operate the SMR process. A third source of emissions, which is typically not caught, is the carbon dioxide and methane produced by the energy necessary to power the carbon-capture equipment.

As previously stated, only two facilities producing blue hydrogen from natural gas will be operational in 2021. As a result, data on the percentage of carbon dioxide that can be captured are scarce. Carbon dioxide captured during SMR has been reported to have efficiencies ranging from 53% to 90%.

Actual data from one of the two commercially running plants, the Shell plant in Alberta, indicate a mean capture efficiency of 78.8 percent, with daily rates ranging from 53% to 90% except for a 15% anomaly. For our baseline study, we use an 85 percent capture rate, which is nearly halfway between the Shell plan’s 78.8 percent and the best-case scenario of 90 percent. Calculating the carbon dioxide produced in SMR at 100 percent minus the capture efficiency:

(15%)*(38.5g CO2 per MJ) = 5.8g CO2 per MJ

That is, after emissions are processed for carbon capture, the SMR process emits 5.8 g CO2 per MJ.

Carbon capture has been limited to the SMR process in commercial blue-hydrogen reactors to far, with no attempt made to capture carbon dioxide created by the burning of natural gas required to supply heat and high pressure. If these combustion emissions are captured, the carbon dioxide capture efficiency may be lower than with the SMR procedure, as the carbon dioxide in the former scenario is more dilute. We are unaware of any statistics on the effectiveness of carbon capture from any plant, including any electric power plant, that burns natural gas, however carbon dioxide capture efficiencies from the exhaust streams of two coal-fired power plants have been reported to range between 55% and 72%. Notably, one of the plants has been seen to operate at up to 90% efficiency when fully loaded. This does not, however, reflect long-term performance, which is determined using an average load. Load is less than full load when carbon-capture equipment is down for maintenance or when demand for carbon dioxide is less than it is at full load. For the sake of this analysis, we utilize a baseline value of 65 percent capture efficiency from flue gases. By subtracting 100 percent from this factor, the emissions from the natural gas used to generate the heat and pressure are as follows:

(35%)*(31.8g CO2 per MJ) = 11.1g CO2 per MJ

Thus, total carbon dioxide emissions from the SMR process, including the energy used to drive the process, range from 16.9 g CO2 per MJ if the combustion flue gases are captured (5.8 g CO2 per MJ plus 11.1 g CO2 per MJ) to 37.6 g CO2 per MJ if the flue gases are not treated (5.8 g CO2 per MJ plus 31.8 g CO2 per MJ).

Nedim Husomanovic

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