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Cows and Eco-construction

Con­crete is the most con­sumed resource on the plan­et, after water. Cement, the key ingre­di­ent in con­crete, has shaped much of our built envi­ron­ment — our hous­es, build­ings, bridges, roads and dams. How­ev­er, its car­bon foot­print is mas­sive. The cement indus­try is one of the pri­ma­ry pro­duc­ers of the green house gas CO2 and accounts for about 8% of the world’s CO2 emis­sions, accord­ing to think tank Chatham House. Con­crete also dam­ages the top­soil, the most fer­tile lay­er of the earth rich in microbes. The hard sur­face of con­crete con­tributes to sur­face run-off that leads to soil ero­sion, water pol­lu­tion and flood­ing. Con­crete and cement pro­duc­tion is high­ly cen­tral­ized, and also cap­i­tal and ener­gy inten­sive. Hence mod­ern con­struc­tion has become a very expen­sive activ­i­ty. Even after con­struc­tion, main­tain­ing the build­ings (heat­ing, cool­ing, light­ing, etc) is very ener­gy inten­sive. Con­struc­tion and build­ings togeth­er account for 39% of the CO2 emis­sions accord­ing to the Glob­al Sta­tus Report of 2017 by the UN Envi­ron­ment and the Inter­na­tion­al Ener­gy Agency.

With the grow­ing aware­ness of the unsus­tain­able nature of con­struc­tion using con­crete, researchers world­wide are work­ing on find­ing sus­tain­able mate­ri­als and meth­ods of con­struc­tion. In this light, let us look at what the tra­di­tion­al knowl­edge of India has to offer, and more specif­i­cal­ly, the sig­nif­i­cance of cows for sus­tain­able con­struc­tion.

Our tra­di­tion­al meth­ods are aligned with nature and hous­es are con­struct­ed with­out dis­turb­ing the trees and water bod­ies in the region. The direc­tion of the wind and nat­ur­al light are care­ful­ly stud­ied in order to reduce the use of air con­di­tion­ers, heaters and lights. Con­struc­tion mate­ri­als are earth-based and local­ly sourced to avoid trans­porta­tion costs. Earth-based con­struc­tion is cost-effec­tive, eco-friend­ly, ener­gy-effi­cient and durable. The cost of Earth-based hous­es are 40% low­er com­pared to con­ven­tion­al hous­es.

Earth-based build­ing mate­ri­als – cob and Adobe The sim­plest and old­est earth-based build­ing tech­nique is cob, which is an amal­ga­ma­tion of soil (dug for the foun­da­tion), clay, cow dung and straw. The pro­por­tion depends on the type of soil in the local region. Cob is a great ther­mal mass, which means that it stores heat ener­gy and releas­es it very slow­ly, thus main­tain­ing a con­stant inte­ri­or tem­per­a­ture even with large tem­per­a­ture swings out­side. It keeps the inte­ri­or of the build­ing cool in sum­mer and warm in win­ter. Con­struc­tion with cob there­fore makes the build­ing ener­gy-effi­cient. Adobe is anoth­er earth-based con­struc­tion tech­nique. Adobe is made from sand, clay, and water, togeth­er with fibrous mate­ri­als like straw and cow dung, which is shaped into bricks using frames and sun-dried.


Adobe mak­ing. (Left) Tamil Nadu (Right) Ladakh

Mud hous­es are struc­tural­ly very strong: they can with­stand severe winds and seis­mic activ­i­ty due to the cir­cu­lar design and thick mud plas­ter. An exam­ple of long stand­ing round mud hous­es in India are the Bhun­ga in Hod­ka, Gujarat. The Bee­hive hous­es in Har­ran, Turkey are made of Adobe entire­ly with­out wood, and date back to 3000 B.C. The ancient Ban­tu civ­i­liza­tion of Africa also built hous­es with mud, poles and cow dung. The round­hous­es in Chal­ton, Eng­land, UK, built more than 2500 years ago and the Native Amer­i­can people’s set­tle­ments in the USA 700 years ago are also exam­ples of last­ing mud con­struc­tions.


Mud and dung hous­es that stood the test of time. (Top left) Bhun­ga hous­es in Hod­ka, Gujarat. (Top right) Round hous­es in Chal­ton, UK. (Bot­tom) Bee­hive hous­es in Har­ran, Turkey.

Cow dung as soil sta­bi­liz­er

Now why is cow dung used in the con­struc­tion mate­r­i­al? Cow dung acts as a good binder and a ther­mal insu­la­tor. The fibers present in cow dung also pre­vent crack­ing. Mod­ern sci­en­tif­ic stud­ies show that cow dung func­tions as a soil sta­bi­liz­er. A soil sta­bi­liz­er is a mate­r­i­al that improves the dura­bil­i­ty of the soil by increas­ing its strength and resis­tance to water. In an inves­ti­ga­tion on the use of cow dung as a soil sta­bi­liz­er in the con­struc­tion of Adobe bricks, bricks with dif­fer­ent cow dung — soil ratios were test­ed for com­pres­sive strength, per­me­abil­i­ty, ero­sion and crack­ing. The results showed that the ratio of 1:4 (cow dung: soil) had the high­est com­pres­sive strength and resis­tance to ero­sion. The ratio 1:5 had the high­est resis­tance to water per­me­abil­i­ty. Fur­ther­more, there was min­i­mum crack­ing in all the treat­ments.

In anoth­er research study, the effects of cow dung on microstruc­tur­al changes in Adobe bricks were inves­ti­gat­ed by the method of X‑ray dif­frac­tion, ther­mal gravi­met­ric analy­ses and scan­ning elec­tron­ic microscopy. It was found that cow dung reacts with kaoli­n­ite and fine quartz to pro­duce insol­u­ble sil­i­cate amine, which glues the iso­lat­ed soil par­ti­cles togeth­er. Also, it was observed that the sig­nif­i­cant pres­ence of fibers in cow dung pre­vents the prop­a­ga­tion of cracks in the brick and rein­forces the mate­r­i­al, lead­ing to a homo­ge­neous Adobe microstruc­ture. There was a sig­nif­i­cant improve­ment in the water resis­tance of the bricks, mak­ing Adobe sta­bi­lized by cow dung an advan­ta­geous build­ing mate­r­i­al for wet cli­mates.


A video microscopy image of cow-dung. Nat­ur­al plant fibres are its major com­po­nent and they have a rough sur­face which enhances the adher­ence between these fibres and the soil in Adobe bricks. This pre­vents crack prop­a­ga­tion and rein­forces the mate­r­i­al, thus improv­ing its mechan­i­cal strength.

Cow urine is also added into the mud while mak­ing a cob/adobe mix as it enhances the prop­er­ty of mud and enables good cur­ing of the soil. Cow urine is also a potent med­i­cine and is used for treat­ing dif­fer­ent ail­ments in Ayurve­da, the Indi­an sys­tem of health.

Tra­di­tion­al plas­ters

Plas­ters are like the skin of a house: pro­tec­tion from tem­per­a­ture and mois­ture. The skin pro­tects the house against heat, rains, winds and ero­sion. Mud plas­ter, mud and lime plas­ter and Vedic plas­ter are some exam­ples. In a mud plas­ter, the com­po­nents of mud them­selves act as binder (fine) and aggre­gate (coarse): the fine clay in mud acts as the binder and the coarse sand acts as the aggre­gate. Fibers like rice husk are added to reduce crack prop­a­ga­tion. Cow dung is added for bet­ter bind­ing and water resis­tance. It also acts as a ther­mal insu­la­tion. In the mud and lime plas­ter, lime, along with clay in mud acts as the binder and sand (in mud) is the aggre­gate. Lime helps to keep ter­mites away. Cow urine is also added for cur­ing which increas­es strength. Vedic plas­ter is a gyp­sum based cow dung plas­ter along with some minor addi­tives. Gyp­sum is used as a heat resis­tant, mois­ture pre­serv­ing, sound absorb­ing and fire proof­ing mate­r­i­al. It is nat­u­ral­ly occur­ring and non-tox­ic and was used in the con­struc­tion of the ancient pyra­mids of Egypt.

Dis­in­fec­tant prop­er­ties

When it comes to floor plas­ter­ing, cow dung is tra­di­tion­al­ly used. Cow dung con­tains 3–5 crores of use­ful microbes. It has anti-fun­gal prop­er­ties and also repels insects. A mud and cow dung paste is applied to floors and also serves to dis­in­fect the floor. Cow urine is also used as an addi­tive for plas­ter­ing floors owing to its anti-fun­gal prop­er­ty. It pre­vents the growth of harm­ful fun­gi on the walls and floors. Cow urine is also an extreme­ly good sealant for earth­en floors. Cow urine is used for seal­ing the top sur­face of the fin­ish, pre­vent­ing crack for­ma­tion.


Tra­di­tion­al paste of cow dung and mud applied to floors.

Mod­ern paints con­tain volatile organ­ic com­pounds (VOCs) which are chem­i­cals inside the paint that are released into the air dur­ing the process of paint­ing. Even though the major­i­ty of VOCs leave the paint as the wall dries, not all of them do; the paint can release VOCs into the air for years after paint­ing. VOCs are dan­ger­ous for health because they are known car­cino­gens (agents that cause can­cer). Accord­ing to the US Envi­ron­men­tal Pro­tec­tion Agency, com­mon­ly used paints con­tain chem­i­cals such as ben­zene, meth­yl­ene chlo­ride and oth­ers that have been linked to can­cer. There­fore, turn­ing to nat­ur­al plas­ters is no longer an option; it is a need.

Neu­ro-cog­ni­tive prop­er­ties and emo­tion­al health

The cow dung in the wall and floor plas­ters also improves mood and reduces depres­sion via inhala­tion of a bac­te­ria that func­tions as an anti-depres­sant. Cow dung is rich in the bac­te­ria Mycobac­teri­um vac­cae. The name of this bac­teri­um orig­i­nates from the Latin word vac­ca mean­ing cow, since it was first cul­tured from cow dung in Aus­tria. which is a non-path­o­gen­ic species that lives nat­u­ral­ly in soil and it is inhaled when peo­ple spend time out­doors, espe­cial­ly in the vicin­i­ty of plants and trees. In 2007, neu­ro­sci­en­tist Christo­pher Lowry and his research group at the Uni­ver­si­ty of Bris­tol, UK, dis­cov­ered that the bac­te­ria acti­vat­ed groups of neu­rons in the mouse brain respon­si­ble for pro­duc­ing the neu­ro­trans­mit­ter sero­tonin, which reduces depres­sion and anx­i­ety. Inter­est­ing­ly, the neu­rons that were acti­vat­ed were also known to be linked to immune response, sug­gest­ing an inti­mate con­nec­tion between the immune sys­tem and emo­tion­al health.


Micro­scop­ic view of Mycobac­teri­um vac­cae, a non-path­o­gen­ic species of bac­te­ria found in cow dung. The bac­te­ria was found to acti­vate neu­rons in the brain respon­si­ble for pro­duc­ing sero­tonin, the neu­ro­trans­mit­ter that reduces depres­sion and anx­i­ety. Inter­est­ing­ly, the neu­rons that were acti­vat­ed were also known to be linked to immune response, sug­gest­ing an inti­mate con­nec­tion between the immune sys­tem and emo­tion­al health.

This bac­teri­um, Mycobac­teri­um vac­cae, is cur­rent­ly being researched and test­ed as immunother­a­py for asth­ma, can­cer, depres­sion, pso­ri­a­sis, der­mati­tis and tuber­cu­lo­sis.

Bovine pow­er

Since ancient times, cows and bul­locks have pro­vid­ed the ener­gy required for con­struct­ing nat­ur­al build­ings. The native breeds of cows are very strong and robust. Hence, they are excel­lent cob knead­ers. The tra­di­tion­al chakku, or the mor­tal mix­ing wheel was also turned by cat­tle. Mor­tar mixed by bovine pow­er is said to be of a very supe­ri­or qual­i­ty, even when com­pared to mor­tars mixed with mod­ern grind­ing equip­ment.

Thus, cows play a sig­nif­i­cant role in nat­ur­al build­ing. The use of cow prod­ucts in build­ing mate­ri­als has been sci­en­tif­i­cal­ly rea­soned and val­i­dat­ed by mod­ern research stud­ies. It is time we trans­late this under­stand­ing into action and active­ly pro­mote cow-based build­ing and liv­ing.

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