TITLE: USING NITROGEN GAS IN PLACE OF CARBON DIOXIDE GAS
AS A COUNTER PRESSURE IN BOTTLING INDUSTRY
FOR COST REDUCTION AND REDUCED ENVIRONMENTAL IMPACT
Beverage bottlers processing carbonated beverages extensively use CO2 – most obviously for carbonation process, but also in a process for maintaining filler bowl counter pressure during the bottling process. Use of CO2 in this process contributes not only to greenhouse gases, but also is a significant cost to the bottler. Nitrogen has already been proven in different parts of the world as an excellent replacement to CO2 in the bottling process and can be done in a significantly cheaper way. This paper presents the findings and summarizes the benefits a bottler may enjoy in switching from CO2 to Nitrogen.
Beverage bottling plants use carbon dioxide gas in two distinct operations. CO2 gas lines are different for both the processes:
a) Carbonation Process – In this process CO2 is mixed with beverages. This dissolved carbon dioxide creates carbonic acid, which adds a pleasantly acidic flavor and an interesting mouth feel.
b) Filler Bowl Counter Pressure Process – In the process of beverage carbonation, CO2 is absorbed under pressure. The CO2 will remain absorbed in solution while it is kept under pressure.
The pressure required to maintain CO2 in the beverage depends on the content required in the beverage and the temperature. Higher CO2 contents require higher pressure at a given temperature and conversely, lower temperatures for a given content require lower pressures.
The filler bowl must, therefore, be kept under the appropriate pressure during the filling process by use of an inert gas. This inert gas itself, typically CO2, does not get further absorbed in the already carbonated beverage solution.
In the filling bowl counter pressure operation to establish an equilibrium pressure inside the bottle, carbon dioxide gas is used and released into the atmosphere on a continuous basis.
It is commonly known and understood that CO2 is a harmful greenhouse gas and it’s increasing concentration in the environment, a major environmental concern. CO2 contributes to extra heat trap in the atmosphere and thereby contributing to ‘Global Warming’.
According to prior submissions of projects to United Nations Framework Convention on Climate Change, (UNFCCC), under program of Clean Development Mechanism (CDM), a project to replace the Carbon Dioxide Gas with Nitrogen Gas in only filling operation for filler bowl counter pressure of a beverage bottling plant in Philippines was approved and implemented.
In the afore-mentioned project nitrogen gas replaced the carbon dioxide gas i.e. used in filling operation as a counter pressure. For the other use of carbon dioxide gas such as for mixing the Carbonated Soft Drinks (CSD) line, it was not included & not affected.
There are several technical and commercial benefits of using Nitrogen as a counter pressure gas instead of CO2:
1. We present below an un-biased comparison of producing nitrogen gas on-site as compared to using CO2 in cylinders purchased from the market.
|Impact Characteristic||On-site production of Nitrogen Gas||Using Carbon Dioxide Gas in cylinders|
|Environmental impact||Power is required to compress the air using an electrical air compressor. The compressed air is then passed through a nitrogen extraction unit, which extracts and purifies the already 78% atmospheric nitrogen. If the electricity used is from the grid, and in-turn if the grid power is supplied using conventional fossil fuels, then the carbon emissions of this electricity generation should be taken into account.||CO2 used from cylinders as the counter pressure gas is directly discharged into atmosphere and hence the environmental impact can be directly calculated from the total volume of CO2 used in the industry.|
|Indirect environmental impact due to trucking||Nitrogen gas is produced on-site and hence there are no associated truck emissions that need to be considered.||Trucks or lorries, if used, to transport the cylinders from the gas merchant to the consumer, also contribute to GHG due to their associated emissions. When calculating the environmental impact, these emissions also have to be considered.|
|Cost impact||Only electricity consumption cost is required to produce nitrogen gas a Nitrogen generator, such as those offered by MVS Engineering. The cost of electricity is significantly lower than the cost of purchasing the same quantity of CO2 or even Nitrogen in cylinders.||CO2 or Nitrogen delivered in cylinders is significantly higher than production of Nitrogen on-site.|
|Space requirement||Nitrogen gas generator requires a small footprint and can be easily installed in the premises. Typically, the space required for stocking bulk cylinders is quite sufficient for installing the nitrogen generator.||For carbon dioxide gas availability the company should plan and manage their cylinders in stock. To ensure that the bottling line does not stop, the companies maintain a significant stock of CO2 cylinders. Large stock of cylinders requires a large ventilated space and storage area footprint is similar to that of a nitrogen generator.|
|Availability management||Nitrogen gas is produced on-demand and may be stored in a small storage tank to ensure continuous uninterrupted supply of nitrogen. The nitrogen generator turns on and off automatically as per usage of gas and no manual handling is required.||Empty cylinders have to be removed and filled cylinders reconnected to the manifold on a continuous basis throughout the day. This is a very laborious task and un-avoidable when using cylinder supplied CO2.|
|Leakage hazard||Negligible chances of leakage of nitrogen gas as only a small volume of Nitrogen is stored for on-demand availability and the gas is stored at a low pressure, typically, lower than 10 bar.||Cylinders generally present a high hazard risk of leakage as the gas stored is at a pressure of 150-200 bar pressure and also repeated handling of cylinders makes them vulnerable to leakage.|
|Maintenance of equipment||Nitrogen gas generators will require periodic maintenance. Maintenance is generally accomplished in a total of 4-hours annually and fairly simple such as filter cleaning, replacement, oil replacement in air compressor etc.||Manifolds will have to be periodically pressure tested to ensure there are no leakages developed over repeated use.|
2. We must also calculate the emission reduction due to avoidance of CO2 use and present a case below on basis of certain data presented earlier.
|S.No.||No. Of Cases/Year Production,|
(1 case= 5.678 ltrs)
|Estimation of baseline emissions|
|Estimation of Project emission|
|Estimation of Emission reduction|
|1||100 million cases/year, (567.8 million ltrs/year)||4628.55||345.05||4283.5|
|2||182 million cases/year, (1033.4 million ltrs/year)||8424||628||7796|
|3||200 million cases/year, (1630.34 million ltrs/year)||9257.10||690.10||8567|
|4||300 million cases/year, (2445.516 million ltrs/year)||13885.66||1035.16||12850.05|
In order to understand how beverage bottlers may benefit from use of Nitrogen in place of carbon dioxide as a counter pressure gas, we must consider the cost of CO2 in cylinders and then compare it against the cost of nitrogen production by an onsite nitrogen generator.
a) Cost of Carbon Dioxide Gas purchased by Cylinders
Present rate of CO2 gas cylinders in Indian market = Rs 50 INR/Kg of CO2 gas.
1 Kg of CO2 gas = 0.5058 Nm3 of CO2 gas, or
1 Nm3 of CO2 gas = 1.97 Kg of CO2 gas
Hence, the cost of 1 Nm3 of CO2 gas in cylinder can be calculated as
1 Nm3 CO2 = 1.97 Kg of CO2 gas x Rs 50 INR/kg CO2.
1 Nm3 CO2= Rs. 98.85 /Nm3 of CO2
b) Cost of Nitrogen gas produced onsite using gas generator
To produce nitrogen gas from an onsite gas generator requires electricity to operate the air compressor and this is the primary variable cost of operation.
For producing 1 Nm3 Nitrogen gas we require only 0.5 KWH electricity power.
If we consider industrial electricity rate of around Rs. 7 / kWh, the production cost of nitrogen by generator can be estimated as Rs 3.50 INR/Nm3
|Consumption||Annual spend on cylinders|
(Cost of CO2 / Nm3 x 7 Nm3 x cylinders per day x 350 days)
|Annual spend to produce nitrogen|
(Cost of N2 / Nm3 x 7 Nm3 x cylinders per day x 350 days)
|Savings per annum|
|10 cylinders / day||!ERROR! undefined variable 'rs'||!ERROR! undefined variable 'rs'||Rs. 23.28 Lacs|
|15 cylinders / day||!ERROR! undefined variable 'rs'||!ERROR! undefined variable 'rs'||Rs. 34.91 Lacs|
|20 cylinders / day||!ERROR! undefined variable 'rs'||!ERROR! undefined variable 'rs'||Rs. 46.55 Lacs|