Bricks Made with Olive Pits Reduce Carbon Footprint of Buildings, Study Finds

Spanish researchers from the University of La Rioja’s mechan­i­cal engi­neer­ing depart­ment use ground olive pits to pro­duce more energy-effi­cient build­ing mate­ri­als.

The researchers demon­strated that using ground olive pits in mor­tar brick man­u­fac­tur­ing can lead to sig­nif­i­cant eco­nomic sav­ings and reduce the envi­ron­men­tal impact of con­struc­tion and build­ing use.

The research ana­lyzed the impacts of dop­ing per­fo­rated mor­tar bricks with ground olive pits in a five to 15 per­cent ratio by vol­ume of fine aggre­gate for build­ing con­struc­tion.

Doping is a tech­nique in which a small quan­tity of a sub­stance is added to a mate­r­ial to alter its prop­er­ties. The method is employed in the man­u­fac­ture of con­struc­tion mate­ri­als to increase their energy effi­ciency, strength, dura­bil­ity, fire resis­tance or cor­ro­sion resis­tance.

In recent years, more research has focused on dop­ing to reduce ther­mal con­duc­tiv­ity, which could lower the energy required to heat or cool build­ings.

Buildings are Europe’s sin­gle largest energy con­sumer. Approximately 40 per­cent of the total energy con­sumed in the European Union is used in build­ings, and around 80 per­cent of the energy used in E.U. homes is for heat­ing, cool­ing and hot water.

Eighty-five per­cent of E.U. build­ings were built before 2000, and 75 per­cent have poor energy per­for­mance. The con­struc­tion sec­tor is, there­fore, seen as cru­cial to achiev­ing the E.U.‘s energy and cli­mate goals.

The study focused mainly on Andalusia, Spain, where large quan­ti­ties of olive pits are pro­duced as a by-prod­uct of olive oil pro­duc­tion.

“My ini­tial inter­est arose from observ­ing the enor­mous vol­ume of waste gen­er­ated by the olive oil indus­try, specif­i­cally olive pits,” said lead author Javier Ferreiro-Cabello.

“These residues have sig­nif­i­cant but under­uti­lized poten­tial in terms of reuse and added value,” he added. ​“In study­ing pos­si­ble appli­ca­tions for these pits, I iden­ti­fied the pos­si­bil­ity of using them to man­u­fac­ture bricks for mor­tar facades. This idea led me to fur­ther inves­ti­gate the fea­si­bil­ity and envi­ron­men­tal impact of this pro­posal.”

The team’s analy­sis showed sav­ings and eco­nomic returns from the medium-term (10 to 20 years) onward by reduc­ing con­ven­tional energy con­sump­tion in heat­ing and air con­di­tion­ing instal­la­tions.

Previous research by Ferreiro et al. has demon­strated that dop­ing with ground olive pit con­cen­tra­tions of up to 30 per­cent can be used with­out com­pro­mis­ing struc­tural via­bil­ity. Concentrations above 15 per­cent were found to increase the eco­nomic recov­ery time beyond the aver­age use­ful life of a build­ing in Spain (70 years).

Several fac­tors were stud­ied to assess envi­ron­men­tal impact. These spanned the full life­cy­cle of the prod­uct, from olive pit grind­ing and its sub­se­quent trans­porta­tion to the pro­duc­tion and trans­porta­tion of doped mor­tar bricks.

When ana­lyz­ing the end pro­duc­t’s net impact over time, the resources used — energy, fuel and water — and the waste prod­ucts gen­er­ated — car­bon oxides, nitro­gen oxides and solid par­ti­cles — were con­sid­ered.

Increasing the per­cent­age of olive pits as a sub­sti­tute for fine aggre­gate was found to raise envi­ron­men­tal impacts in most cat­e­gories, except for water usage.

Higher olive pit con­tent low­ers the water impact because nat­ural aggre­gate pro­duc­tion requires sub­stan­tial water for inter­nal wash­ing processes.

A 15 per­cent dop­ing with olive pits resulted in a 7.98 per­cent reduc­tion in water con­sump­tion, sav­ing 0.61 cubic meters per square meter of the facade.

In the global warm­ing cat­e­gory, a 4.68 per­cent increase in CO2 emis­sions was cal­cu­lated for 15 per­cent dop­ing, equat­ing to 0.8 kilo­grams of CO2 per square meter of facade. This increase was due to the higher energy and resource con­sump­tion needed to incor­po­rate olive pits.

Categories related to nat­ural aggre­gate pro­duc­tion, includ­ing acid­i­fi­ca­tion, eutroph­i­ca­tion, and pho­to­chem­i­cal oxi­da­tion, saw increases of 29.13 per­cent, 30.28 per­cent, and 21.56 per­cent, respec­tively. The olive pit prepa­ra­tion process, involv­ing energy and mate­r­ial use for crush­ing and trans­port, caused these impacts.

Transport processes were found to sig­nif­i­cantly affect recy­cled aggre­gates’ via­bil­ity, increas­ing nitro­gen oxides, car­bon oxides and solid par­ti­cles that impact the ozone layer.

A 15 per­cent dop­ing showed an 8.90 per­cent increase in ozone layer deple­tion and an 8.19 per­cent rise in fos­sil fuel deple­tion, equiv­a­lent to 6.90 mega­joules per square meter of facade.

When cal­cu­lated over a 35-year period, how­ever, the increases in energy use and emis­sions asso­ci­ated with the ini­tial man­u­fac­tur­ing process were more than off­set by the over­all sav­ings.

The analy­sis showed that over this period, the net energy cost of 15 per­cent-doped mate­r­ial man­u­fac­ture was below zero, and the CO2 emis­sions were also below zero for all build­ing energy sources. This lat­ter was most remark­able for build­ings using elec­tri­cal power sources, with a reduc­tion of 105.84 per­cent.

However, the authors stress that the ben­e­fits of olive-pit dop­ing are lim­ited to regions where olive waste is abun­dant and local, as trans­port is a sig­nif­i­cant con­trib­u­tor to energy usage and emis­sions. Thus, increased trans­port would result in sig­nif­i­cantly fewer ben­e­fits.

They also note that this is only one of many exam­ples of the indus­try’s poten­tial for increased sus­tain­abil­ity.

“The cir­cu­lar econ­omy will play a key role in the future of con­struc­tion by offer­ing sus­tain­able and effi­cient solu­tions to address envi­ron­men­tal and eco­nomic chal­lenges,” Ferreiro said. ​“By adopt­ing prin­ci­ples of reuse, recy­cling and waste reduc­tion, the con­struc­tion indus­try can min­i­mize its envi­ron­men­tal impact and max­i­mize resource use.”

“In the spe­cific con­text of my research, the use of olive pit waste in the man­u­fac­ture of facade bricks is a clear exam­ple of how the cir­cu­lar econ­omy can trans­form an indus­try’s by-prod­ucts into inno­v­a­tive and sus­tain­able build­ing mate­ri­als,” he added.

Many ini­tia­tives to increase sus­tain­abil­ity in the build­ings and con­struc­tion sec­tors are in place world­wide.

These range from multi­na­tional pro­grams such as the United Nations’ Sustainable Development Goal 12 and the European Union’s Strategy for Sustainability in Construction and Renovation Wave pro­grams to leg­is­la­tion at national and local lev­els.

However, Ferreiro believes that much more can be done.

“The gov­ern­ment can play a cru­cial role in encour­ag­ing research and devel­op­ment in the field of sus­tain­able con­struc­tion through sup­port­ive poli­cies and pro­grams,” he said. ​“This could include finan­cial incen­tives for com­pa­nies invest­ing in research and devel­op­ment projects related to the cir­cu­lar econ­omy and sus­tain­abil­ity in con­struc­tion.”

“In addi­tion, the gov­ern­ment could estab­lish reg­u­la­tions and stan­dards that pro­mote the use of recy­cled mate­ri­als and the adop­tion of sus­tain­able prac­tices in the con­struc­tion indus­try,” Ferreiro con­cluded. ​“Education and aware­ness pro­grams could also help sen­si­tize key stake­hold­ers to the impor­tance of sus­tain­abil­ity and the cir­cu­lar econ­omy in con­struc­tion.”

• European Commission