Investigation on the use of co-products from olive oil industry in earth bricks

Abstract

In 2020, an estimated 3.2 million metric tons of olive oil was produced worldwide. Producing also a similar amount of a solid and liquid coproducts consisting mainly of pomace and olive mill wastewater. These by product are generally untreated and discharged immediately into the environment which consists a major ecological issue for olive oil-producing countries due to their high toxic organic loads and low pH. Morocco is one of the countries facing this issue. Actually, we are highly ranked in the world in terms of production and exploitation of products from the olive sector which constitutes 5% of our national agricultural Gross Domestic Product (GDP). Furthermore, the building sector in Morocco represents 33% of the energy consumed nationally. Thereby, the construction industry must adapt to new trends and environmentally sustainable construction systems, thus requiring lines of research aimed at keeping energy consumption in new buildings as low as possible. In this context, this work presents a review of the state of the art concerning the uses of coproducts from the olive industry in construction materials, more specifically fired and unfired clay bricks. First, we went by the chemical composition of the coproducts taking into consideration the used process of extraction. In fact, olive oil can be extracted through discontinuous or continuous processes. In both processes yield three fractions: a solid residue and two liquid phases (oil and olive mill wastewater). We surveyed several academic research that showed that these coproducts are mainly composed of phenolic compounds, carbohydrates, organic acids and mineral nutrients variably distributed depending on the process employed and the agronomic practices. Then, we discussed and expounded the physical, mechanical and thermal properties of bricks reinforced by olive oil coproduct. In particular, we outlined that with olive oil coproduct we can produce light, porous earth bricks with good thermal performance.