CO2 Emissions Comparison

CSEB vs Fired Bricks in Nepal

2018-04-18

Global Overview

Research by Auroville Earth Institute, the world-renowned research institute on earthen structures, have shown that CSEB (Compressed Stabilised Earth Bricks) emits “13 times less CO2” than the Country Fired Bricks (CFB) during production. Additionally, their comparison for the CO2 emission for walls shows that CSEB emits “4 times less CO2” than the Kiln Fired Brick (KFB) and “9 times less CO2” than the Country Fired Brick1. Other researchers, globally, have also confirmed on the findings; stating that CSEB emits roughly one tenth of the CO2 emissions compared to fired bricks during production2,3,4.

CO2 emission rate for CSEB compared to Fired Bricks Source: Auroville Earth Institute

CSEB in Nepal

Despite the undisputable findings that CSEB has significantly better environmental performance than fired bricks, the above figures are based on CSEB of size 24X24X10 cm, using 5% cement as stabilizer, and non-interlocking system which requires 10mm mortar. However, the CSEB used in Nepal are mainly of size 30X15X10cm, using 10% cement stabilizer, and in interlocking system which requires only 5mm of mortar.

Differences between Auroville Research and construction with CSEB in Nepal

Auroville Nepal

Type of construction: Public buildings

& ‘beautiful design’ Low cost housing & reconstruction

Width of wall: 24 cm6 15 cm5

% Cement in prod.: 5% cement6 10% cement5

Type of CSEB: Non-interlocking CSEB Interlocking CSEB5

Thickness of mortar in wall construction:

10 mm 5 mm

Different ratio for mortar: 1:4:8 (cement, sand, soil)6 1:4 (cement & sand)

The differences in the production of the bricks and difference in construction guidelines for different countries produces different CO2 emission rates. Thus, to make an accurate CO2 comparison for CSEB in Nepal, we need to make a comparison based on the production and construction standards of Nepal.

CO2 Emission of CSEB and Fired Bricks produced in Nepal

Each unit of CSEB is produced by mixing sand, soil, and 10% cement and compressed in a manual machine. Before starting production, the local soil is tested for its sand content and then extra sand is added to the mix to reach a total sand content of 60%. The sand and soil are sourced locally with no or very limited transportation. Thus, the CO2 emissions from the cement is the most relevant factor for CO2 emissions by CSEB. According to Auroville the production of CSEB with 5% cement stabilization emits 49,366 KgCO2/m36. So accordingly, in our calculation for production of CSEB we are assuming that CSEB produced with 10% cement stabilization will emit 98,7 KgCO2/m3 6. As per the same research paper from Auroville, the national average of CO2 emissions for kiln fired bricks in India is 202.255 KgCO2/m3 and we are assuming a similar CO2 emission by the kilns in Nepal6.

CO2 Emissions in Construction

There are important differences in construction with CSEB compared to Fired bricks in Nepal:

• CSEB has a larger brick size and less width of wall; meaning less units of CSEB are needed to build the same length of wall (both in number of units and in volume)7

• 50% less cement and sand mortar needed in construction as7: o Interlocking CSEB requires 5mm mortar in between bricks and fired bricks requires a

minimum of 10 mm up to 20mm8 o CSEB walls has a nice finish and allows the house-owner to paint directly on the wall, while

fired brick houses are most commonly plastered in Nepal7 All our calculations and the quantity of material is based on Nepal National Building Code NBC – meaning a cement-mortar mix ratio of 1:4 for walls and 1:6 for wall plaster8. Another important difference is that CSEB houses are required to be built on stone-mortar foundation5, while fired brick houses can be built using either stone-mortar or brick-mortar foundation9.

Differences in Construction of CSEB and Fired Houses in Nepal

CSEB Nepal Fired Bricks Nepal

Type of construction: CSEB Load bearing wall design Fired Brick Load bearing wall design

Size of Brick: 15x30x10 cm5 22x11x5,5 cm9

Width of wall: 15 cm5 22 cm9

CO2 emissions in prod.: 98,7 KgCO2/m36 202.255 KgCO2/m36

Thickness of mortar in wall: 5 mm mortar Min. 10 mm up to 20 mm mortar8

Ratio for mortar in wall: 1:4: (cement & sand) 1:4 (cement & sand) 8

CO2 emission per 3.5 room house in Nepal

*All quantities of material is based on Nepal National Building Codes: http://www.buildupnepal.com/wp-content/uploads/2018/04/Construction-material-comparison-CSEB-Fired-Bricks-2018-1.pdf

** All KgsCO2/m3 data is based on values from Auroville Earth institute: http://www.buildupnepal.com/wp-content/uploads/2018/04/Embodied-Energy-of-Various-Materials-and-Technologies-S-Maini-V-Thautam-Auroville-

Earth-Institute-2009-1.pdf

Conclusion

As per the calculation, we can conclude that 5,63 tonnes of CO2 (44% reduction) and 3,54 tonnes of CO2 (33% reduction) can be deducted when a 3.5 room of 33.3 square meters CSEB house is built instead of a fired brick house with brick-mortar foundation and stone-mortar foundation respectively. As there are no reliable figures available on the ratio of fired brick houses built with stone-mortar foundation and brick-mortar foundation respectively, it can be argued for an average number that would be to count 50% for each foundation type. Then the weighted national average CO2 reduction for building a 3.5 room CSEB house compared to a 3.5 room fired brick house is 4 580 kg, or 4.58 tonnes of CO2 less which equals to a total reduction of CO2 by 39%.

Item Fired Brick House

(stone mortar foundation)

Fired Brick House (brick mortar foundation)

CSEB House

Fired Bricks / CSEB* 10 042 23 702 2 371

m3 size of bricks 0,0013 0,0013 0,0045

Total m3 of bricks 13,4 31,5 10,7

KgsCO2/m3 of brick type** 202,3 202,3 98,7

Kgs of CO2 for bricks 2 703 6 381 1 053

Cement sand mortar (1:4) - m3* 19 19 11,25

Cement sand mortar for plastering (1:4) 3,4 3,4 0

KgsCO2/m3 of cement sand mortar (1:4)** 178,5 178,5 178,5

Kgs of CO2 for cement sand mortar 3999 3999 2008

Aggregate - m3* 7 7 6

KgsCO2/m3 of aggregate** 58 58 58

Kgs of CO2 for aggregate 406 406 348

Stones for foundation - m3* 42 4 42

Kgs CO2 per m3 of stone** 41,6 41,6 41,6

Kgs of CO2 for stone 1747 166 1747

Iron Bars – kg* 613 613 667

Kgs CO2 per m3 of iron bars** 3,0 3,0 3,0

Kgs of CO2 for iron bars 1839 1839 2001

Total CO2 emissions in ton 10,69 12,79 7,16

CO2 reduction by CSEB 3,54 5,63 Weighted average CO2 reduction in ton per CSEB house

4,58

http://www.buildupnepal.com/wp-content/uploads/2018/04/Construction-material-comparison-CSEB-Fired-Bricks-2018-1.pdfhttp://www.buildupnepal.com/wp-content/uploads/2018/04/Construction-material-comparison-CSEB-Fired-Bricks-2018-1.pdfhttp://www.buildupnepal.com/wp-content/uploads/2018/04/Embodied-Energy-of-Various-Materials-and-Technologies-S-Maini-V-Thautam-Auroville-Earth-Institute-2009-1.pdfhttp://www.buildupnepal.com/wp-content/uploads/2018/04/Embodied-Energy-of-Various-Materials-and-Technologies-S-Maini-V-Thautam-Auroville-Earth-Institute-2009-1.pdfhttp://www.buildupnepal.com/wp-content/uploads/2018/04/Embodied-Energy-of-Various-Materials-and-Technologies-S-Maini-V-Thautam-Auroville-Earth-Institute-2009-1.pdf

References

1 - Auroville Earth Institute, http://www.earth-auroville.com/compressed_stabilised_earth_block_en.php

2 - Walker, P. J. (1995). Strength, durability and shrinkage characteristics of cement stabilised soil blocks. Cement and concrete composites, 17(4), 301-310.

3 -Riza, F. V., Rahman, I. A., & Zaidi, A. M. A. (2010, December). A brief review of compressed stabilized earth brick (CSEB). In Science and Social Research (CSSR), 2010 International Conference on (pp. 999-1004). IEEE.

4- Waziri, B. S., & Lawan, Z. A. (2013). Properties of compressed stabilized earth blocks (CSEB) for low-cost housing construction: a preliminary investigation. International Journal of Sustainable Construction Engineering and Technology, 4(2), 39-46. 5 – Vol 2 of Earthquake resistant model houses, DUDBC, Department of Urban Development and Building Construction. http://www.dudbc.gov.np/uploads/default/files/a1efdb9058f9151775d9a2bae473ac0b.pdf 6 – Embodied Energy of Various Materials and Technologies, S Maini, V Thautam - Auroville Earth Institute, 2009. http://www.buildupnepal.com/wp-content/uploads/2018/04/Embodied-Energy-of-Various-Materials-and-Technologies-S-Maini-V-Thautam-Auroville-Earth-Institute-2009-1.pdf

7 - Construction material comparison required for 3.5 room house - CSEB-Fired-Bricks-2018. http://www.buildupnepal.com/wp-content/uploads/2018/04/Construction-material-comparison-CSEB-Fired-Bricks-2018-1.pdf

8 - ”Mortar joints should not be more than 20mm and less than 10mm in thickness. The ratio recommend 1:4 (Cement: Sand).” Volume 1 of Earthquake resistant model houses, DUDBC, Department of Urban Development and Building Construction. Page 125. http://www.dudbc.gov.np/uploads/default/files/0ef9f3598df115407ae9ed4e7bfab24a.pdf 9 – Vol 1 of Earthquake resistant model houses, DUDBC, Department of Urban Development and Building Construction. http://www.dudbc.gov.np/uploads/default/files/0ef9f3598df115407ae9ed4e7bfab24a.pdf

http://www.earth-auroville.com/compressed_stabilised_earth_block_en.phphttp://www.dudbc.gov.np/uploads/default/files/a1efdb9058f9151775d9a2bae473ac0b.pdfhttp://www.buildupnepal.com/wp-content/uploads/2018/04/Embodied-Energy-of-Various-Materials-and-Technologies-S-Maini-V-Thautam-Auroville-Earth-Institute-2009-1.pdfhttp://www.buildupnepal.com/wp-content/uploads/2018/04/Embodied-Energy-of-Various-Materials-and-Technologies-S-Maini-V-Thautam-Auroville-Earth-Institute-2009-1.pdfhttp://www.buildupnepal.com/wp-content/uploads/2018/04/Construction-material-comparison-CSEB-Fired-Bricks-2018-1.pdfhttp://www.buildupnepal.com/wp-content/uploads/2018/04/Construction-material-comparison-CSEB-Fired-Bricks-2018-1.pdfhttp://www.dudbc.gov.np/uploads/default/files/0ef9f3598df115407ae9ed4e7bfab24a.pdfhttp://www.dudbc.gov.np/uploads/default/files/0ef9f3598df115407ae9ed4e7bfab24a.pdf