What does a GHG Inventory for a dye house look like

“Rough” GHG Inventory for a “one line” dyeing and printing unit.

A)?????Caveat

A GHG Inventory is a serious business. There is a precise protocol to follow which may, and actually has to, give different results depending on the mill it is considering. The protocol has the advantage of being public and “as certifiable” as any protocol (take any quality certification, for example). No “higgies” to be evaluated by one organisation, no compulsory consultants. Although transparency can be disputable at any level of the textile Industry, the GHG protocol is in my opinion a correct approach to the greenhouse gas emission measurement problem.

We are consultants. We cannot disclose data which belong to our customers. Therefore what you will find here below is a reasonable picture of what a GHG Inventory of a dyeing and printing unit should look like in reality, but the data do not refer to any specific mill. Moreover, we consider only the most important emissions as for scope one, that is the generation of thermic energy to produce steam (the boilers). Please also note I did not consider any efficiencies, as again this depends heavily on the mill’s set up and age. On the other hand, we are very conscious energy efficiency in a mill can be as important as 40% of its emissions.

Data regarding solar energy are again coming from Pangea data base, and refer to actual projects we are working on. There is no running CSP project that I know in the textile industry, yet.

The scope of this paper is simply to give a general picture of the “average situation”, and we take full responsibility of any mistake. In fact, we suggest any reader who would like to compare its situation to what we picture here below and find un-reasonable differences to contact us, so that we may fine tune the data as much as possible.

B)?????A generic textile mill, processing cellulosic fibre fabrics.

Let us take into consideration a “one line” dyeing and printing unit:

1.??????One Continuous Bleaching Range (CBR) desizing and bleaching

2.??????One merceriser

3.??????Two Continuous Cold Pad Batch dyeing lines

4.??????Two dye and print wash lines

5.??????4 jiggers

6.??????One rotary printing unit

7.??????Two stenters running with thermic oil (out of the scope of this paper)

8.??????Two sanfor units

In decent production conditions, such a unit would process approximately 2,3 million meters / month, 24/7 running hours, say 300 Grams per Linear Meter (GLM) average fabric weight (mix of shirting and bottom wear). That would be 23 tons of fabric, daily.

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C)?????Electrical and thermic energy requirement, including power for a biological Effluent Treatment Plant, NOT Zero discharge (no final evaporator and Reverse Osmosis).

This mill would require approximately 950 KW electric power and approximately the equivalent of 11 tons of steam per hour at 3,5 bars. We are not considering thermic oil for stenters, as for now. These data come from an average of the data of three different mills, very similar to each other.

Maths would give a daily requirement of:

·??????950 x 24 = 23 MWh of electric energy

·??????11 x 24 = 264 tons of steam as for thermic energy.

According to OWiD, here are the carbon intensities of electric kwh provided by different national grids.

Let us assume the plant is in Pakistan, where a kwh coming from the national grid generates 296 grams of CO2 emissions. Let us also consider and Indian site, where the national grid generates 626 gr of CO2 per kwh.

The 23Mwh of the electric power we need daily to run this plant will emit 23.000 kwh x 0.296 = 6.808 kgs of CO2, say 7 tons of CO2 daily in Pakistan, approximately 14 tons in India, if it takes its power from the “national grid”.

Now, the thermic power.

1 ton of saturated steam requires approximately 696 kwh of energy, no specific efficiency of boilers considered.

264 tons correspond to 264 x 696 = 183 MWh of thermic energy, daily. Let consider two different fuels and check the corresponding CO2 emissions.

·??????Natural Gas: 183 MWh x 201.96 = 37 tons of CO2 daily

·??????Charcoal: 183 MWh x 403.2 = 74 tons of CO2 daily.

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In short, the CO2 emission coming from the boilers are five to ten times the emission coming from electric power requirement of our dyeing and printing mill (7 vs. 37 or 7 vs. 74), depending on the fuel used to fire boilers. In case of India, numbers change, as we would have a range of more than the double (14 vs. 37) to five times (14 vs. 74).

Whatever the case, speaking in terms of the GHG protocol for a textile process house, scope one emissions are far more important than scope two, according to these numbers. But this is not the only point.

One may say that a single small/medium company such as this cannot do much to improve the emissions of its electric power requirement. Let alone co-generation for the sake of simplicity (it does not change much as for GHG emisisons), the mill can only take what its grid gives. The mill management could, as an option, invest in windmills or another CO2 neutral source and get them branched to the national grid or directly to the mill, if possible. According to GHG protocol, it might so be entitled to declare reduction of its scope two emissions. On the other hand, there are things which can be done on its own thermic generation, that is the way it runs its steam boilers, which represent the majority of its scope one emissions.

A first step would be to move from fossil fuels such as coal or methane to biomass (rice husk or wood waste?). As per internationally accepted criteria, emissions would be “carbon neutral”, in that case. It is my opinion that burning biomass emits CO2 anyway, and that it means a lot of damage in terms of pollution, as anyone living in Delhi (or Lahore) may confirm. Burning rice husk in a boiler with appropriate filters is different than burning agriculture waste on the fields (the Delhi pollution), but I think we should leave the carbon?trapped in biomass to agronomics, or processes and industries that do NOT emit Green House Gases at all, let alone 2,5M particulate.

D)????The solar energy option.

One possible path is solar energy. State of the art brings us to two options: photovoltaic panels and concentrated solar power.

The big difference between PV and CSP stands in the capacity of the two different technologies to intercept solar irradiation. PV grabs 28% maximum, CSP manages to intercept up to 60%, in the same given conditions. In one case you get electric energy, in the second thermic energy.

Say we have approximately 10.000 square meters of roof and that we are, say, in Lahore, the place where solar Direct Normal Irradiation (DNI) is unfortunately the lowest in Pakistan.

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These 10.000 square meters, geared up with Concentrated Solar Power (CSP) technology would generate 4.400 MWh of thermic energy in a year. As per graph here above, this energy would fluctuate according to the season, but as an average, this means 4.400 / 350 = 13 MWh daily.

Roughly, the same surface would provide 6,5 MWh (electric) daily in case of PV plant, because of the bare different interception capacity of the two technologies. If our mill was in Pakistan, this would save 1,9 tons of CO2 emissions (6500 kwh x 0,296 gr of CO2 scope two), if it was in India, this would save 4 tons of CO2 emissions (6500 x 0,626 gr of CO2 scope two).

If we consider CSP and thermic energy (SCOPE ONE), daily savings fluctuate between 2,6 tons of CO2 (13 MWh x 201.96 kgs of CO2, in case of natural gas) and 5,2 tons (charcoal) of CO2 depending on the fuel of our boilers. The choice is ours.

If we consider thermic energy, 10.000 square meters dedicated to CSP would provide 8% of this “one line” dyeing and printing unit, and the project would be scalable according to the surface available for the CSP mirror area. (Our “one line” mill will probably have approximately 15.000 to 20.000 square meters of roof available, without considering land around the plant). If our mill were in Karachi, where DNI is approximately 20% more than Lahore, we could reach 11% of this mill thermic needs. If we moved to Ahmedabad, India, where DNI is almost 30% more than Lahore, we probably can reach 13% to 15%.

Finally, what is the economics of the solution, which takes away 10% to 15% of this mill scope one emissions?

Considering nowadays cost of the natural gas in Pakistan today (88 USD/MWh) and the investment required for the CSP plant, the payback is less than 7 years, which is probably less than a brand-new biomass boiler, although biomass cost fluctuates as much as fossil fuels, nowadays. Most importantly, the above numbers refer to 10.000 square meters of mirror reflecting area. The biggest the area, the better is the payback (but higher the initial investment).

Finally, thermic energy can be easily stored. Imagine a situation in which, because of wider surface allocated to the CSP plant and lower running requirement (think at a denim finishing and dyeing mill), solar thermic generation exceeds the requirements. Hot thermic oil can be stored in insulated tanks, which would enable our mill to run for some time during the night, as well. No expensive lithium batteries required.