For a Hungarian saw-mill, the CO2 gas mass has been estimated which has been generated by its construction and continuous operation. As measuring tool for the extent of CO2 pollution, the forest area was assessed which would absorb the exhaust gases emitted by the mill during its existence. The mill had been erected on an area of 6 hectare [ha], and has been in operation for 90 years. The mass of CO2 released into the air during this period was calculated to be roughly 105´340 t, while the gas mass still to be set free during a proposed rehabilitation time of 25 years was calculated to be a further 28´725 t, totalling 134´100 t CO2 for the 115-year period of interest. In order to remove this mass of gas from the atmosphere during the suggested 25 years, an afforested area of roughly 1’341 ha was needed. After 25 years rehabilitation time, the forest area could be reduced to 281 ha which would cater for the mill´s future yearly CO2 output. The redundant 1´160 ha may be sold to cover the expenses spent on the remedial measures. Financially, it might bring a light profit if it was realized as a joint venture by the mill, the host-community and a trust. The insight gained from this example is, however, rather disturbing.
Method Article
The CO2 balance of a sawmill
https://doi.org/10.21203/rs.3.rs-2010164/v1
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CO2-pollution
CO2-balance
CO2-capturing
saw-mill
environment rehabilitation
In order to generate a CO2-balance for a saw-mill, the following logic was applied: In preindustrial times, the ground area of saw-mills had been covered by forests. Accordingly, the forest area size ought to be determined based on its CO2-capturing capacity which would equal the mill’s exhaust gas mass, discharged into the air as from its start up to the end of the rehabilitation time.
Any disturbance of gas concentration in the atmosphere strives for natural adjustment. Consequently, CO2 released at any point on the earth will globally increase the overall concentration with time. This additional gas volume can be assessed for each individual company. If this amount of CO2 would be retracted from the atmosphere at any location, the increased atmospheric pollution caused by the mill might be undone.
Alongside CO2, emission gases from any source also contain other chemical compounds such as methane, water vapour, nitrous oxide, sulfuric composites, etc. (Takashiro, A., 2018). In the balance, they will show up as CO2 equivalents (Fay R. et al., 2000; Perruchoud D.O. et al., 1999). With the exception of water vapour and methane, all compounds are to a lesser or greater degree poisonous to living creatures, and they collectively contribute to the global warming, make rain water and oceans acidic, endanger the ozone layer, and otherwise degrade the environment (Wackernagel M. et al., 1996; IPCC, 2014). Thus, immediate actions ought to be considered.
Planting forests is one of the effective remedies. In order to determine the area size, the CO2-balance of the mill – as detailed below - shall serve as a guide.
Methods
The mill´s CO2 balance can be assessed by Equation 1, and contains following entries:
CO2/af = CO2/spcet + (ST + RT) * (CO2/la + CO2/op) [t] (Eq.1)
Legend:
[t] - metric ton,
[y] - year,
CO2/af - gas mass [t] which shall be removed from the atmosphere via photosynthesis with the help of afforestation during a given rehabilitation time,
CO2/spcet - gas mass [t], generated by site clearance, preparations, construction, equipment and technology renewal,
ST - service time [y], duration of CO2 emission by the mill´s operation,
RT - rehabilitation time [y], designated to remove all CO2 generated by the mill,
CO2/la - lost CO2 absorption capacity of the forest cleared for the mill [t/y],
CO2/op - gas mass [t/y], emitted during the production of energies needed for the operations.
In the followings, an example shall be detailed. The values calculated stand for assumptions and approximations, may thus create an imperfect picture about the pollution, but they shall give some information about the magnitude of numbers involved. If needed, a more precise CO2 balance can be worked out another time, according to the contemporary state of the arts.
For the mill’s CO2 balance following assumptions have been made:
Preparations (CO2/spcet)
Site clearance: The mill had been erected 90 years ago on a 6 ha large area, originally covered by forest. The trees were felled by manpower. One tree was cut, pruned and sawn to logs by two workers in approximately one hour. Their power output, expressed in physical units, may have been about 100 Watt (Luczak H. et al., 2010). In order to clear six hectares of forest with about 250 trees/ha, an estimated 300 kWh ([1],[2],[3],[4]) energy was spent. As a consequence of felling and removal of all trees from the 6 ha forest, 0,75 t CO2[5] was released into the air.
One log was pulled out from the forest presumably by one horse and one worker in about 15 minutes. The physical work spent amounted to 28 kWh[6] which corresponds to 0,07 t CO2 for the whole log volume.
90 years ago the transport may have been carried out with the help of horse carriages. From 6 ha, about 1´500 t logs[7] were collected. These logs required 188 wagon loads, each carrying 8 t timber. Loading timber onto and from a wagon, respectively, was performed by five workers in two hours. The according energy consumption amounted to 188 kWh[8], i.e. 0,47 t CO2.
The wagons delivered the timber to the merchant about 15 km away, so a round trip was done in one day. Using two horses per carriage, the according CO2 emission may have amounted to 2´214 kWh[9], or 5,54 t CO2.
Summing up, the site clearance and the log transport consumed approximately 2´730 kWh energy, and released roughly 7,0 t CO2[10] into the atmosphere. It was also assumed that the logs had been used for lumber production, and were not incinerated on site.
Site preparation and creation of infrastructure[11]: The data, as meticulously collected and calculated as above according to the method of Lockie, S. et al. (2012), yielded another 22 t CO2.
Construction and equipping of buildings as well as technological renewal generated about 1´380 t CO2[12]. Additional furniture, computers, etc. had generated further 520 t CO2[13].
Summing up, buildings and equipment polluted the air with 1´929 t CO2 already at the start (values in boxes will be used in the Equations 1 and 2).
Service time (ST) specifies the period during which the mill has been in operation. According to the mill´s records, it started 90 y ago, and will run still for an undefined number of years.
Rehabilitation time (RT) refers to the management´s decision according to which a forest plantation for a period of 25 y shall be established. During this period the forest shall purify the atmosphere from as much CO2 gas as the mill might have emitted during its service life and the rehabilitation time. In the years thereafter, the mill has to still be aided by the plantation to remain pollution free.
Operations (CO2/op): The mill has processed 30´000 m3 logs per year. The yearly energy consumption amounted to roughly 450 MWh[14] which is equivalent to 1´125 t CO2.
Lost CO2 absorption capacity (CO2/la): Forests absorb on average about 4 t/(ha.y) carbon dioxide via photosynthesis, and converts it to an organic substance (Enssle J. 2010). On the 6-ha area, however, where the mill is standing, the forest is missing. The according loss of possible CO2-capture equals 24 t/y.
With the above data, following two questions can be answered:
(1) What was the total amount of carbon dioxide pumped into the air during the period of interest, i.e. 90 y of operation and 25 y of rehabilitation times?
The answer is given by Equation 1:
In short, 105´340[15] t CO2 mass has been released by the mill during its 90 years of existence, and an additional 28´725 t gas mass can be expected within the 25 years rehabilitation time - altogether roughly 134´100 t.
(2) What size of forest area would be needed to bind this amount of gas and convert it to trees during 25 years?
The answer is delivered by Equation 2: Calculated for 25 years, the area size of the forest plantation with an expected CO2 removal capacity from the air of 4 t/(y.ha) amounts to:
Plantation Area Size ≈ 134´100 [t] / (4 [t/(y.ha)] * 25 [y]) ≈ 1´341 [ha] (Eq.2)
Thus, in order to remove the 134´100 t CO2 generated by the plant during its 90 year service life and the 25 years remedial period, an area of 1´341 hectare must be afforested. Basically, this plantation would deploy its advantageous effect as from the very first year of its establishment with increasing effectivity. Cultivated henceforth sustainably, the CO2 balance would tilt back to the favour of the environment and to the relief of the company after 25 years.
In order to compensate for future air pollution, roughly 281 ha[16] forest must be retained. With regards to the original goal, the remaining 1´160 ha would become redundant, and could be sold to another company struggling with the same problem. Thereby, a substantial part of the initially invested money may get reimbursed while the volume of carbon dioxide generated by the mill has been eliminated from the atmosphere. This is a temporary remedy, however, and remains effective until the wood gets burned at disposal, or would rot away.
A Possible Implementation
The acquisition of 1´341 ha fertile ground, its afforestation and cultivation represent a big investment for a relatively small company. Nevertheless, with common effort, it could even become financially profitable. The endeavour needs to be a joint venture with participants such as the company, the host-community and a trust.
The company with its small area is responsible for 5%[17] of the 1´341 ha afforestation. This outlay is an investment for the mill which cannot be passed over to the customer in form of higher selling price of products because the customer has contributed to the same objective already in form of taxes (see at host-community). Thus, this expenditure must be deduced from the company’s reserves.
The host-community (town, province, or state) enjoys the advantages of the company’s presence. The company provides jobs, produces required goods, and most importantly, it pays taxes. Thus, the community ought to be morally obliged to participate in the venture. Generally, the community must not seek an immediate profit of such an investment, it can wait with the hope for a later gain and with the comforting conviction that it has contributed to the rehabilitation of the environment. Its share in the expenditures could be as large as the overall tax ratio in the region, say 40%.
A trust would endow the remaining funds. Together with the company and the community, it will be responsible for the purchase of the ground, for the afforestation and the upkeep of the plantation, and it has to provide the financial base in form of securities, stocks and bonds with a hope for an ensuing financial gain. The share of the trust is the outstanding 55%. The security papers of whatever kind could be traded, inherited, deposited, donated, etc. meaning that these would not be long-term investments, these could be sold with a small profit. Even ordinary people could afford to acquire these, granting the documents wide spread.
With the passing 25 years, the forest would have fulfilled its purpose, and 1’160 ha might be sold. The returns would be apportioned among the shareholders according to their contribution. Calculations suggest that the enterprise could become profitable if the above-mentioned forest area was sold for three times the original purchasing price (Bariska M. et al., 2015). Taking into account the possible rise of the property value, the value increase of forest, and inflation, this is not an unrealistic scenario after 25 years. As a result, the air was purified and the investors received their profit.
In subsequent times, the company, the community and the trust still remain the owners of the residual 281 ha forest which is needed to compensate for the mill’s ongoing CO2 emission. Should the plant terminate its production activity, the leftover forest area can be sold as well. Thus, environment rehabilitation mustn’t be a losing deal.
[1] 300kWh = 2 [worker] * 0.1 [kW/worker] * 1 [hours/tree] * 250 [trees/ha] * 6 [ha][2] 1kWh = 3.6 MJ (MegaJoule), physical unit of work (energy). For reasons of convention, we use kWh (kiloWatt.hour) and not Megajoules
[3] Generally, it is assumed that during the production of 1 kWh energy in a coal powered plant 1 kg CO2 emerges. Other authors state that 4.5 kg was a more realistic number (Lockie S. et al. 2012; Taffese, W.Z., et al. 2019; Hoxha, V., 2020). In our calculations, we use a value of 2.5 kg CO2 per one kWh energy generated.
[4] In our calculations, we use a value of 2.5 kg CO2 per one kWh energy generated.
[5] 0,75 t ≈ 300 [kWh] * 2.5 [kgCO2/kWh]
[6] 28 kWh ≈ 0.736 [kW horsepower/horse] * 1 [horse] * 1 [worker] * 0.1 [kW/worker] * 250 [log/ha] * 6 [ha] * 0.25 [h/log]
[7] 1´500 t ≈ 250 [logs/ha] * 6 [ha] * 1 [ton/logs])
[8] 188 kWh ≈ 188 wagon * 2 [hour/wagon] *5 worker * 0.1 kW/worker ]
[9] 2´214 kWh ≈ 188 trips * (0.736 [kW horsepower/horse] * 2 horses * 8 hours
[10] 6,83 t
[11] Estimated value based on the items’ weight = 21.6 t CO2 (Taffese, W.Z., et al. 2019; Hoxha, V., 2020)
[12] 1´380 t CO2 = Sawmill 390 t (750 m2 à 0.52 t CO2/m2), offices 196 t (450 m2 à 0.435 t CO2/m2), sales offices + exhibition hall 87 t (200 m2 à 0.435 t CO2/m2), warehouse 64 t (400 m2 à 0.16 t CO2/m2), workshops, garage, dryer, steamer, energy producing plant 464 t (850 m2 à 0.545t CO2/m2) } * 1,15 (1,15 stands for value adding by renewals on three occasions /see also Bariska M., Pásztory Z., 2015/)
[13] using the above calculation procedure
[14] Mill´s data
[15] 105´339 t ≈ 1´929 t + 103´410 t
[16] 281,25 ha ≈ 1125 [t/y] / 4 [t/(y.ha)]
[17] The percentages are arbitrarily chosen. They may assume any value which the participants would agree upon
These numbers show that already a small sized mill will cause considerable disruption in the environment. A sawmill is, however, not the only kind of industry. The world is full of other factories with their oozing chimneys. To compensate for the roughly 35 giga[18].t CO2 global emission (Grant, D.S, 2020) per year an additional forest area of about 1 billion.ha was needed, and a staggering 4 billion.ha for the restitution of damages done in the past, in other words, the present forest area of the planet ought to be doubled (Williams M., 2006) . Regrettably, the forest area of the earth continues to diminish also in the future, some areas becoming even unfit for afforestation (Gálos B. et al., 2011) But perhaps by other means, e.g. by future inventions, a stop or even a partial reversal of this frightening development might be still possible (e.g. by large scale technical removal of CO2 from the atmosphere). Let’s believe in the ingenuity of future engineers and in the creativity of politicians.
This example suggests three kinds of insight: Firstly, we discover that timber processing, as one of the least environment-impairing industry activities, represents already a reckless intrusion on nature, and that man - despite his conviction that he was working competently and professionally - inevitably causes deep wounds in the environment. Secondly, that in the future, everyone might compulsorily pay for the recuperation of damages done to nature (possibly in form of taxes). Thirdly, that there isn´t any time to waste.
[18] giga = billion = 1´000´000´000 x
Ethics approval and consent to participate
During the research no ethical issues was touched, neither human or animal cell or organ. The research restricted only carbon-dioxide calculation done by the authors excusively.
Consent for publication
The authors contribute to the publication.
Availability of data and materials
Most of the initial data either come from the cited literature or well-known trivial data. The calculations are written and the results can be follow in the text.
Competing interest
No competing interest pops up in this article.
Funding
This research was founded by the TKP2021-NKTA-43 project.
Authors contributions
Original method was worked out by Mihály Bariska, the calculation test run by Zoltán Pásztory. The funding was provided by the organization of the second author.
Acknowledgement
This article was made in frame of the project TKP2021-NKTA-43 which has been implemented with the support provided by the Ministry of Innovation and Technology of Hungary (successor: Ministry of Culture and Innovation of Hungary) from the National Research, Development and Innovation Fund, financed under the TKP2021-NKTA funding scheme.
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No competing interests reported.