Utilizing Waste Derived from Elaeis guineensis (African Oil Palm) for Partial Cement Replacement in Stabilizing Compressed Earth Blocks

Abstract

The increasing demand for sustainable construction practices necessitates innovative approaches to reduce the environmental impact of conventional building materials like cement. African oil palm waste, abundant in palm-producing regions, represents a promising alternative material. This research explores the feasibility of utilizing waste materials derived from Elaeis guineensis (African oil palm) as a partial cement replacement in the stabilization of compressed earth blocks (CEBs). This study involves the collection and preparation of shells from oil palm waste for use in compressed earth block (CEB) production. Various proportions of these waste materials are mixed with conventional soil and cement to assess their impact on CEB properties. Compressive strength, durability, and environmental considerations are key parameters evaluated in this investigation. Preliminary findings suggest that incorporating oil palm waste in CEBs can enhance their compressive strength and reduce the carbon footprint associated with cement production. Moreover, this approach has the potential to address waste management issues in palm oil-producing regions while promoting sustainable construction practices. The research contributes to the development of eco-friendly building materials and aligns with global efforts to mitigate the environmental impact of the construction industry.

1. Introduction

In the pursuit of sustainable and environmentally conscious construction practices, researchers and practitioners have increasingly turned their attention to innovative solutions that minimize resource depletion and waste generation. This chapter delves into a promising avenue within this realm by investigating the potential utilization of waste derived from Elaeis guineensis, commonly known as the African oil palm. The focus here lies in its application as a partial replacement for cement in the stabilization of compressed earth blocks (CEBs). This approach holds the promise of addressing two critical concerns simultaneously: the responsible disposal of agricultural waste and the enhancement of earth-based construction techniques.

The urgency of sustainable construction practices cannot be overstated. Traditional building methods often rely heavily on resource-intensive materials such as cement, contributing significantly to carbon emissions and depleting finite natural resources. In this context, exploring alternative materials that not only curtail these detrimental impacts but also harness agricultural waste is of paramount importance. Elaeis guineensis, a tree widely cultivated in various tropical regions for its oil-rich fruit, has emerged as a focal point for such exploration.

The utilization of waste derived from Elaeis guineensis presents a unique opportunity to transform a potential environmental burden into a valuable resource. The African oil palm industry generates substantial quantities of waste, including empty fruit bunches, palm kernel shells, and fibers. These by-products, if not managed properly, can contribute to pollution and environmental degradation. However, they also possess characteristics that make them potentially suitable for various applications, including construction materials.

Compressed Earth Blocks (CEBs) offer a sustainable and low-carbon alternative to conventional bricks or concrete blocks. By stabilizing the soil with cement, lime, or other binders, CEBs provide durability and strength while minimizing the need for resource-intensive materials. This chapter investigates the viability of incorporating waste from Elaeis guineensis into the binder matrix of CEBs, thus serving a dual purpose of enhancing the blocks’ properties and diverting agricultural waste from landfills or open burning.

The multifaceted benefits of this approach extend beyond waste management and resource conservation. The use of agricultural waste in construction materials can contribute to rural economic development by creating new markets for these materials and promoting sustainable practices within the agricultural sector. Additionally, by reducing the reliance on cement, which is a significant contributor to greenhouse gas emissions during its production, this innovative solution aligns with global efforts to mitigate climate change.

As we delve deeper into this chapter, we will explore the mechanical and environmental aspects of incorporating Elaeis guineensis waste into CEBs. Through a combination of experimental analysis and theoretical considerations, we aim to provide a comprehensive understanding of the potential advantages, challenges, and considerations associated with this sustainable construction approach. By shedding light on the practicality and effectiveness of utilizing waste from the African oil palm in earth-based construction, we hope to contribute to the ongoing dialog surrounding environmentally conscious building practices and inspire further research and adoption of innovative solutions in the field.

2. African oil palm and its waste

Approximately three decades ago, the global production of oil palm experienced a nearly threefold increase. By the period of 2009–2010, the anticipated worldwide output of palm oil was projected to reach 45.1 million tons. Notably, Malaysia and Indonesia collectively contributed 85% to this production, each yielding more than 18 million tons. A report from the United Nations Economic and Social Commission for Asia and the Pacific (UN ESCAP) identified Indonesia and Malaysia as the principal contributors to the substantial presence of oil palm residues in Southeast Asian nations.

The extraction of oil from fresh fruit bunches leads to the generation of liquid and solid by-products, including fiber, shell, and seepage. Consequently, issues pertaining to pollution of the air, rivers, oceans, and groundwater have escalated due to the disposal of these waste materials. The responsible and effective management of agricultural by-products becomes imperative for the advancement of sustainable practices.

To mitigate environmental pollution stemming from oil palm cultivation, the principle of the “zero waste policy” must be extended to by-products. This entails utilizing empty fruit fibers for fuel and employing the ash as fertilizer. Historically, waste derived from the shells of African Oil Palm, more commonly known as Palm Kernel Shells (PKS), has been inadequately managed and often discarded near mills. Research indicates that PKS aggregates possess an abrasion value of approximately 4.8%, along with significantly lower impact and crushing values compared to conventional crushed stone aggregates. Consequently, PKS exhibits potential as a construction by-product.

Recent developments have seen the incorporation of palm kernel shells in the construction of access roads for oil palm mills. However, there is a paucity of published reports regarding their performance. Palm Kernel Shells (PKS) are acquired through the crushing or threshing of palm fruit to extract palm seeds subsequent to palm kernel oil extraction. Significant volumes of palm kernel shells are produced in Ondo State and Edo State, Nigeria, with moderate quantities available in other regions, particularly in the South.

Due to their inherent hardness, PKS demonstrates resilience once integrated into concrete, thereby minimizing the release of contaminants or toxic substances. Furthermore, PKS obviates the need for the processing of artificial aggregates or industrial by-products before their application, a distinction from certain artificially manufactured aggregates and industrial by-products.

The process of oil extraction at the mill industry generates both liquid wastes and solid residues. The endocarps of palm kernel shells (PKS), due to their sturdiness and hardness, fulfill the role of safeguarding palm kernels, which exhibit considerable variation in size and shape. With their natural lightweight characteristics, these shells offer a potential alternative for coarse aggregates in lightweight construction applications. Their intrinsic hardness and organic composition render them suitable for integration into concrete production, and their matrix-like structure minimizes the likelihood of contaminant release or formation of harmful substances. Notably, PKS-based lightweight concrete presents advantages over aerated concrete, as it exhibits lower permeability and reduced susceptibility to carbonation.

Palm kernel shells display an irregular shape after cracking, lacking a distinct and uniform definition. The cracks on the shells exhibit a range of forms, including semi-circular, parabolic, uneven, and flaking. While the overall contour of the shell demonstrates convex and concave features, the edges become coarse and spiky upon cracking. The thickness of the shell is found to vary, contingent upon the originating species, typically falling within the range of 2 to 3 millimeters.

Numerous studies have incorporated PKS as aggregate in concrete production, resulting in notable transformations in lightweight concrete (LWC) structures. Notably resilient, the shells resist deterioration even after being submerged for 24 hours, with water absorption capacity increasing by 21 to 33%. In comparison with conventional gravel aggregates, PKS displays higher water absorption capabilities. When incorporated into an accurately formulated mix design, PKS can effectively enhance the properties of concrete with an average strength of 20 to 30 MPa. In contrast, limited research has explored the potential of PKS for masonry purposes, particularly as bricks.

Over time, the construction of sustainable housing in numerous developing countries has frequently relied on clay mud. This housing approach is particularly favored by individuals with moderate to low incomes. The current landscape of housing development poses a significant challenge due to the substantial financial investments it demands. Additionally, when considering environmental factors, the feasibility of utilizing industrial waste in infrastructure development becomes apparent, given that these materials adhere to established standards and specifications. Efforts are being directed toward identifying alternative applications for industrial by-products, rather than allowing them to decay unused. The exploration of environmentally friendly material recycling and energy conservation has gained prominence in recent decades. Conversely, the surge in environmental regulations has heightened the demand for eco-friendly materials within the construction sector. A continuous investigation is imperative to ascertain the potential of palm kernel shells (PKS) for the production of masonry blocks. It is viable to partially replace traditional aggregates with PKS in the creation of sand-concrete blocks.

Wastes originating from the oil palm industry are often discarded without any profitable utilization, resulting in adverse environmental impacts. PKS encompasses particles of varying sizes: 0–5 mm, 5–10 mm, and 10–15 mm. In addition to posing challenges for disposal and waste management, these shells lack commercial value. The integration of palm kernel shells into construction practices is not prevalent in Ghana; local blacksmiths employ them as fuel, and they can serve as fillers or palliatives.

2.1 Applications of palm kernel shells

Various palm species, such as Dura, Pisifera, and Tenera, exhibit distinctions in their shells, fibrous oily components, and fruits primarily attributed to differences in thickness. Specifically, the Dura type is characterized by a slim fibrous component and an extensively thick shell. In contrast, the Pisifera variety typically possesses a minute shell or none at all, largely due to its fibrous nature, resulting in limited or negligible kernel production. The Tenera species combines attributes of both Dura and Pisifera, featuring a moderately thick shell and a medium-sized fiber component.

Palm kernel shells are put to the following uses:

1. Essential as a significant fuel source for domestic cooking in various regions.

2. Generally treated as waste materials within the oil industry and subsequently discarded.

3. Employed by blacksmiths and goldsmiths to create bellows for the purpose of iron/gold melting.

4. Potential for producing terrazzo materials using palm kernel shells.

5. In some areas, utilized to fill potholes within muddy terrain.

6. Possibility of generating pre-stressed concrete through lightweight aggregates derived from shells, offering valuable thermal insulation.

3. Incorporating African oil palm shell ash (palm kernel shell ash) for earth block stabilization

Compressed earth blocks (CEBs), commonly referred to as compressed stabilized earth blocks (CSEBs), encompass compact brick elements with well-defined properties, obtained by compacting soil within a wet mold and promptly demolding. The cohesion of CEBs is influenced by the clay content within the soil. CSEBs, a refined variant of CEBs, are augmented through the inclusion of additives. As CEBs are sensitive to water, additives are introduced to counteract this effect. These additives not only address color and shrinkage cracks but can also modify other attributes. Additionally, CSEBs can be known as stabilized soil blocks (SSBs), Stabiblocs, Terracretes, Soilcretes, or Pressed Soil Blocks (PSBs).

Modern CSEBs evolved from molded soil blocks, also known as adobe blocks. Initial iterations of CSEBs employed wooden tamps, elevating the quality of molded earth blocks. Although the concept of enhancing strength through soil compression is not novel, the development of motor-driven, mechanical, and manual compactors in the 1970s and 1980s facilitated the emergence of the compressed earth block industry. Earth is the oldest building material, yet its popularity waned with the advent of modern construction materials and techniques until the energy crisis prompted its resurgence. Growing environmental concerns have further spurred the utilization of soil as a global building material.

CSEBs offer numerous advantages over alternative building materials [1]:

1. It leverages local materials, reducing transportation expenses and fostering local economic activity.

2. Construction is swifter and requires less skilled labor, yielding stronger, better-insulated, and thermally efficient structures.

3. Waste levels are minimal, and disposal is straightforward.

4. Environmental pollution is negligible.

5. Energy efficiency and eco-friendliness, reducing energy use and emissions. The production phase generates fewer carbon emissions and lower embodied energy.

6. Local production, reducing costs and promoting sustainability.

7. Durability against harsh weather conditions when properly designed and constructed.

8. Mitigation of deforestation, as CSEB production does not require firewood.

9. Adaptability to diverse technical, esthetic, cultural, and social needs.

10. Transferable technology that is easy to learn and requires semi-skilled labor.

11. Job creation, especially for less skilled and unemployed individuals.

12. Market viability, often cheaper than fired bricks, dependent on local context.

13. Reduction in imports, owing to local production and unskilled labor utilization.

14. Flexible production scales, spanning from manual to motorized tools.

15. Cost-effectiveness, stemming from local production and minimal transport.

Earth remains a primary building method in many developing countries, being easily accessible, cost-effective, and suitable for unskilled individuals. Its high thermal insulation, fire resistance, and thermal comfort contribute to its appeal. Earth-based construction methods, such as adobe blocks and wattle and daub, have been used for centuries. Moreover, compressed earth, a blend of soil and stabilizers compacted under high pressure, enhances performance and strength, despite the inherent heavy and weak properties of soil.

Durability challenges persist in earthen houses, prompting suggestions from past researchers for enhancing the strength and durability of earth raw materials. Strategies include using stabilizers, appropriate architectural design, reinforcing with bonding mortar, and applying protective plaster or render. While rendering, paint, or plaster can shield a compressed earth block or housing wall from external threats, their cost and disparities in expansion rates between these materials and soil blocks pose limitations.

4. Methodology (laboratory preparation and results)

Palm kernel shells were dried in sunlight and burnt following BS specifications. Two types of blocks, Control Mix Block (CMB) and Cement-PKSA Block (CPB), were produced using lateritic soil. The variables included cement-PKSA ratio, compaction pressure, and curing conditions. CMB was stabilized with 10% cement, while CPB was prepared with mix ratios of 8:2, 6:4, 4:6, and 2:8 (Cement: PKSA). Compaction pressures of 6 and 10 MPa were applied to create 66 CMB and 528 CPB of dimensions 100 x 100 x 100 mm. The blocks underwent curing at 100% humidity followed by 28 days of secondary curing. Wet and Dry Compressive Strength tests (WCS and DCS) were conducted according to BS standards. The influence of mix hold-back times (5, 30, 60, 90, and 120 minutes) on compressive strength was examined. Block Dry Density (BDD) and Total Water Absorption (TWA) were also determined as per BS specifications. The data were statistically analyzed using ANOVA at α0.05.

For CMB at 6 MPa, WCS was 8.99 MPa, while CPB values were 9.84, 7.51, 5.29, and 3.21 MPa for mix ratios of 8:2, 6:4, 4:6, and 2:8, respectively. At 10 MPa, CPB exhibited values of 10.11, 8.41, 6.72, and 5.76 MPa, respectively. DCS values at 6 MPa for mix ratios of 8:2, 6:4, 4:6, and 2:8 were 11.79, 9.66, 7.33, and 4.61 MPa, respectively. These surpassed the recommended standards of 3.00 and 4.12 MPa for WCS and DCS, respectively. An inverse relationship was noted between WCS and hold-back time; WCS values were 5.28, 5.13, 4.41, 2.59, and 2.07 MPa for hold-back times of 5, 30, 60, 90, and 120 minutes, respectively. BDD for CMB and CPB at 6 MPa was 2128 ± 0.33 kg/m³ and 2132 ± 0.095 kg/m³, respectively, and 2127 ± 0.01 kg/m³ at 10 MPa, meeting the required 2000 kg/m³ standard. TWA was 7.5% for CMB and 7.0% for CPB, both within the 12% standard. A 44% TWA decrease and 2.3% density increase were achieved with variations in cement content from 2 to 8%. The correlation coefficient and P-values were significant, indicating a positive relationship between BDD and WCS, and a negative relationship between TWA and BDD for both CMB and CPB.

Thus, palm kernel shell ash proves suitable as a partial cement replacement for producing compressed stabilized earth blocks.

5. Waste to wealth opportunity

Throughout history, waste derived from agricultural and industrial activities has led to challenges related to waste management and environmental contamination. Nonetheless, the construction industry has the potential to harness the practical and cost-effective advantages offered by these agricultural and industrial waste materials [2]. These waste materials, often available locally and lacking commercial value, result in minimized transportation expenses [3]. Particularly in the realm of economical construction, agricultural waste materials can offer advantages over conventional alternatives. By incorporating waste materials into construction processes, the conservation of natural resources and environmental safeguards are promoted. Despite the considerable difficulties associated with the disposal and handling of industrial and agricultural waste, their utilization not only safeguards resources but also contributes to environmental preservation and reduces construction expenditures. This approach becomes viable due to the availability of waste materials at negligible or no cost, resulting in substantial contributions to the conservation of natural resources and the ecological equilibrium.

Given the substantial presence and volume of waste products worldwide, environmental risks and disposal challenges have come to the forefront. Nigeria’s “Waste to Wealth policy” provides a framework for treating waste materials and subsequently utilizing them to enhance or stabilize soils with suboptimal geotechnical properties, particularly expansive soils. Many of these materials are sourced locally from traditional industrial and agricultural waste, including Palm Kernel Shell Ash (PKSA), maize cobs, Saw Dust Ash (SDA), coconut shell ash, rice husk, Locust beans ash, and Cocoa Pod ash. Typically, these materials originate from milling facilities, thermal power plants, and waste management installations [4, 5, 6].

Scientific exploration has delved into the feasibility of integrating agricultural waste materials into both building construction and civil engineering projects. Additionally, within the realm of oil palm manufacturing, specific waste products warrant consideration. One such by-product is Palm Oil Fuel Ash (POFA), which emerges from palm fruit residues derived from oil palm trees. The oil palm industry utilizes fresh fruit bunches as its primary raw material, yet the processing of these bunches generates substantial waste, including empty fruit bunches, shells, and fibers. Following the extraction of oil from the palm fruit bunches, roughly 70% of raw waste is produced. This waste can be classified into three categories: fruit-kernel shells, fiber husks, and gels. Notably, kernel shells and fiber husks are burned as fuel in oil palm mills, generating energy within the temperature range of 450 to 600 degrees Celsius. Subsequent to combustion, approximately 15% of solid waste materializes as oil palm fuel ash and palm kernel shell ash. The ash’s color varies from light to dark gray shades, contingent on its carbon content, with uniformity achieved through pulverization. Notably, there have been endeavors to substitute fine aggregate with palm kernel shell ash, often employing palm oil fuel ash as an admixture due to the pozzolanic properties of palm kernel shell ash when combined with cement.

6. Conclusion

In the pursuit of advancing sustainable construction practices, the exploration of unconventional materials and innovative techniques emerges as a pivotal avenue for shaping the trajectory of the built environment. This chapter has undertaken a meticulous examination of the feasibility and potential merits associated with utilizing waste sourced from Elaeis guineensis, or the African oil palm, as a partial cement substitute within the context of compressed earth block stabilization. Through an intricate dissection of the benefits, challenges, and practical implications inherent in this approach, it becomes discernible that this novel methodology holds substantial promise for significantly influencing sustainable construction practices.

The amalgamation of Elaeis guineensis waste into the stabilization process of compressed earth blocks embodies a dual-purpose solution: It effectively addresses the imperative matter of waste management in the palm oil production industry while concurrently augmenting the mechanical and thermal attributes of the resultant construction blocks. This symbiotic synergy encapsulates the core ethos of sustainability by mitigating environmental impact while concurrently enhancing structural integrity. The comprehensive examination spanning scientific, engineering, and pragmatic domains demonstrates a compelling pathway toward a more ecologically conscious and resource-efficient paradigm in the construction domain.

Concluding this discourse, it emerges that the utilization of Elaeis guineensis waste as a partial cement replacement within compressed earth block stabilization represents not a singular panacea but rather a fragment within a broader panorama. It epitomizes the convergence of diverse disciplines encompassing agricultural practices, waste management protocols, material science intricacies, and construction engineering methodologies, all coalescing toward the common aspiration of sustainable progress. The success intrinsic to this innovative approach resides not solely in the confines of laboratory innovation but equally in the successful transposition of these innovations to real-world contexts, where their true potential is effectively harnessed.

Ultimately, the integration of waste materials from Elaeis guineensis into the process of stabilizing compressed earth blocks highlights the effectiveness of working across different fields, innovative thinking, and careful planning. By adopting this new method and understanding its core ideas, the construction industry is ready for a significant change. This change represents a shift where environmental challenges are reduced, the ability to withstand challenges is strengthened, and the overall structure of the built environment aligns with the principles of sustainability. This transformation benefits both the current generation and those to come.