Furniture manufacturing is one of the oldest industrial activities worldwide, and technological advances have enabled its manufacturing system to evolve and increase in scale.
Worldwide, 77 percent of furniture production is concentrated in 10 countries, with Brazil being the 6th-largest producer. This manufacturing sector generates a large volume of wood waste (WW) from the processes of cutting and sanding, for which the main raw materials are solid wood and wood panels.
The Brazilian wood furniture industry represents 80 percent of the furniture production units in the country. There were a total of 17,900 industries that produced 372 million pieces of furniture in 2022. Notably, approximately 30 million tonnes of WW are generated annually in Brazil. Therefore, proper management of WW has become an important goal.
WW management should consider WW as an input for the production of materials and energy. An analysis of 49 studies indicated that the generation of heat and electricity is common; in relation to wood products, reconstituted panels such as medium-density particleboard (MDP) and medium-density fibreboard (MDF) are the most investigated.
However, many places in the world still send WW to landfills; this practice should not be prioritized, due to the accompanying generation of leachate, greenhouse gas (GHG) emissions, reduced landfill life, and wasted land use.
The circular economy (CE) is an economic model that describes practices whereby waste is avoided by encouraging its return to production processes or directing it toward new production cycles that can recover its value. This process provides options for reusing and recycling materials.
In this context, the concept of industrial symbiosis proposes a connection between production units in which the waste from one unit is adopted as a raw material by another unit.
In the study carried out by Cárcamo and Panãbaena-Niebles, Brazil stood out as the leader in the number of research projects in the Americas (81%), which is significant for an emerging economy. However, the contaminants in WW can hinder its use in a CE.
To ensure quality, it is necessary to separate potential contaminants from potential materials. In this way, the proper handling and classification of WW enhances its circularity.
Life-cycle assessment (LCA) is a widely used tool for identifying environmental gains in WW management strategies. In this context, LCA is a methodology that supports CE and, thus, supports robust decision-making for a CE model.
Managers in the furniture industry in the state of Espírito Santo (ES), located in the southeastern region of Brazil, lack a systemic vision regarding the full value of this manufacturing sector. This includes knowledge of each stage of the product’s life cycle, from the extraction of raw materials to final disposal.
The vast majority of companies in the state work in a linear production system, where their waste is disposed of in landfills or incinerated. This type of manufacturing is contained in a paradigm where the main stages are extraction, production, use, and disposal; this process is reaching its limit.
The furniture sector in Espírito Santo has 479 establishments, of which 417 produce furniture using predominantly wood materials. Another characteristic of this furniture segment is the number of small companies, which account for 55 percent of all manufacturing units in the state.
In the north-central area of the state, the spatial focus of this research is the furniture hubs of Colatina and Linhares, which together account for 75 industries.
The Linhares furniture centre occupies a prominent position nationally in the manufacture of mass-produced furniture, while the Colatina furniture centre traditionally focuses on the production of custom-made furniture.
An annual generation of 80,000 tonnes of WW has been estimated for these two furniture hubs, which can vary from one year to the next due to market fluctuations.
Most of the waste generated is destined for firing in the kilns of the red ceramics industry. In addition, a wood panel industry is located in the far north of Espírito Santo, which is one of the main suppliers of raw materials to the furniture industry.
This relationship supports connections between manufacturing units based on the concept of industrial symbiosis, which enables units to work together on a regional or local scale; synergies between industries are detectable and transport distances are feasible in technical and economic terms, thus allowing waste to substitute for natural resources.
The aim of this study was to carry out a comparative LCA, analysing the environmental aspects and impacts of different WW management scenarios generated in the furniture industry of Espirito Santo, with the north-central area of the state as the spatial focus of the research.
The following WW management scenarios were studied: MDF production, MDP production, solid ceramic brick production, heat production in the ceramics industry (current practice), and landfill disposal.
In addition, the products and energy generation were compared with the predominant market scenarios that use virgin sources. To the best of the authors’ knowledge, no other LCA study has provided a broad overview of different alternatives for managing WW from the furniture industry, projecting scenarios based on the industrial synergies of a given region.
Furthermore, this research included wood panel waste in its analysis, which is still minimally studied. This research focuses on a Brazilian region, but it is intended to contribute to future studies to be conducted in other locations.
Theoretical Background
The basic raw materials of the wood furniture industry are solid wood and wood-based materials such as plywood, veneer, MDF, MDP, and oriented strand board (OSB).
Part of these raw materials is lost in manufacturing in the form of waste, which is estimated at 10 percent of the total mass. However, a study carried out at a medium-sized furniture industries in Espírito Santo showed a percentage loss of over 20 percent.
The technical feasibility of using WW has been proven by many studies. Buschalsky and Mai investigated the recovery of wood fibre from post-use MDF waste via thermohydrolytic disintegration, which proved the viability of this process up to the third generation of panels.
Teixeira researched the combined use of MDP waste and fresh residual wood to manufacture new MDP panels, concluding that all of the product’s properties remained preserved. Other studies have considered 100 percent natural WW as a raw material for the production of MDP.
In addition, Mori et al. found that adding up to 11 percent WW was feasible without altering the technical properties of solid ceramic bricks.
Kim and Song applied LCA to evaluate the performance of WW recycling systems for the production of particleboard and combined heat and power generation, and the results showed a greater benefit for the production of particleboard.
Hossain and Poon carried out an LCA of the current practice in Hong Kong of disposing of WW in landfills compared to three proposed scenarios that included the use of chipboard, wood–cement board, and energy production.
The authors concluded that generating energy from WW was the best strategy for environmental gains when compared to generating energy from coal.
Sormunen et al. conducted a comparative study with various construction waste products, including wood, for the manufacturing of thermoplastic composites; this study covered environmental and economic aspects based on LCA and accounting principles, respectively.
The results of the environmental analysis showed that the use of WW compared to plastic waste in the production of composites had lower benefits due to the lower impacts avoided from its disposal.
In addition, Pinho and Calmon conducted a broad critical review of the literature on the LCA of WW management systems. The results showed that although the research followed ISO standards, it was possible to verify the lack of standardisation and clarity in relation to how the LCA methodology is applied in investigations centred on the environmental analysis of WW management systems.
Scenarios Evaluated
Five scenarios were evaluated: three material product production scenarios (MDF, MDP, and solid brick), one energy product production scenario (heat in the ceramics industry—the current practice), and one landfill disposal scenario.
The three materials were compared to the predominant products on the market (made solely from virgin sources), and the energy product was compared to that made from virgin wood.
After being collected and transported to the material product manufacturing sites, the waste is treated before it can be used. In this way, the virgin resources are replaced by 20 percent in the panels and 11 percent in the ceramic brick on a mass basis (w/w).
As MDP is not yet manufactured in the region’s panel factory, we considered its production data to be equal to MDF production, i.e., 1200 cubic metre per day and 30,000 cubic metre per month.
For the production of ceramic bricks and heat, we considered the sum of the production of the industries belonging to the ceramic industry cluster in northern Espírito Santo, represented by the most important municipalities: Colatina and São Roque do Canaã.
These municipalities border one another, and most of the industries are close to one another. Solid brick has a daily production of 13 tonnes. To generate heat, the production of these industries averages 800 tonnes of ceramic products per day.
In the MDF and MDP manufacturing process, biogenic CO2 emissions resulting from wood fuel in the boiler were assumed to be neutral, as eucalyptus, which has a short rotation time in Brazil, would have absorbed an equivalent amount of emissions during its growth process.
Regarding the transportation of supplies, CONAMA/2018 Resolution 490, which was used to define the Euro 6 system as of January 2023, was adopted. This legislation aims to achieve significant reductions in pollutant emissions from diesel-powered vehicles.
The allocation procedure used in this study was process subdivision (also called cutoff criteria) in the generation of WW at the furniture factory to disregard the upstream environmental load.
The main characteristics of the scenarios studied are described below.
Scenario 1
The production of MDF with 20 percent w/w waste (S1-20 percent WW) was considered, with 10 percent GA and 10 percent GB, including virgin wood (80 percent w/w), and then compared to MDF produced with 100 percent virgin eucalyptus wood (S1-100 percent NW).
The reference flow was the production of one cubic metre of uncoated MDF with a thickness of 15 mm, an average density of 690 kg/cubic metre, and a moisture content of eight percent w/w.
In this scenario, the furniture industry sorts the WW, determining the type and quantity of waste available for collection. The WW is then collected by trucks and taken to the panel factory in Pinheiros.
The waste is deposited in a dry place and then sent for treatment. GA waste goes through an electric chipper and sieving to obtain wood chips. GB waste is recycled using the thermohydrolytic disintegration method, as described by Buschalsky and Mai. After appropriate treatment, the waste is used as a raw material in the manufacture of MDF.
Primary data collection for the foreground inventory took place at the MDF factory in Pinheiros, with the managers responsible for each production area, in 2020 and 2022.
A material flow analysis (MFA) was carried out to check the mass balance of the materials in the process via STAN software version 2.6.801. The difference between inputs and outputs was 1.36 percent w/w, which falls within the maximum range of five percent reported in the literature.
The data for the foreground inventory of MDF production were constructed using primary sources, which were collected directly from the industry. Emissions to air, land, and water were inventoried on the basis of emissions reports for the industry studied, made available by IBAMA, the Ministry of Cities, and Piekarski et al.
Scenario 2
The production of MDP (particleboard) with 20 percent w/w waste (S2-20 percent WW) was considered, with 5 percent MDP waste, 15 percent solid WW, and virgin wood (80 percent w/w), and then compared to MDP produced with 100 percent virgin eucalyptus wood (S2-100 percent NW). T
he percentage of waste adopted for this analysis followed the Brazilian study by Teixeira. The latter study also notes that, with a proportion of five percent MDP residue, new boards can be produced without changing the technology and losing their quality. The two MDP panel scenarios analysed used data from Silva et al.
Waste from the Linhares and Colatina furniture industries is transported to the panel factory in Pinheiros, Espírito Santo. The reference flow is the production of one cubic metre of uncoated MDP with a thickness of 15 mm, an average density of 630 kg/cubic metre, and a moisture content of eight percent w/w.
In this scenario, the furniture industry sorts the WW, determining the type and quantity of waste available for collection. The WW is then collected by trucks and taken to the panel factory in Pinheiros. The waste is deposited in a dry place and then sent for treatment.
The GA and GB waste goes through an electric chipper and sieving to obtain the appropriate particle size (2–20 mm). The waste is then used as a raw material in the MDP manufacturing process.
For S2-20 percent WW and S2-100 percent NW, electricity consumption, raw materials, and chemical dosages were also adopted. In addition, Silva and Silva et al. indicated that 75.5 kg of waste is required to meet the boiler’s energy needs per cubic meter of MDF; this research was conducted considering these data, which resulted in more environmentally friendly production results for the MDP studied, similar to those of the Brazilian MDF produced in the state of Espírito Santo.
As MDP was not produced at the panel factory in this study, the foreground inventory was established based on the work of Silva et al.
Scenarios 3 & 4
Scenario 3 considers the production of ceramic bricks with 11 percent w/w waste (S3-11 percent WW), with the same proportions of GA and GB, and 89 percent w/w clay; these bricks are then compared to ceramic bricks produced with 100 percent clay (S3-100 percent NC).
The firing fuel for the brick made with waste is also based on WW (GA + GB), while in the brick made with 100 percent clay, virgin eucalyptus is chosen as the energy source.
WW from the Linhares and Colatina furniture industries is transported to the ceramics factories in Colatina and São Roque do Canaã, ES. The reference flow is the production of one kg of solid brick.
The furniture industry sorts the WW, informing the ceramic factories of the type and quantity of waste available for collection. The WW is then collected by trucks and taken to the ceramics industries in São Roque do Canaã and Colatina.
The waste is deposited in a dry place and then sent for treatment. Then, it is put through an electric chipper and sieved to obtain the appropriate particle size (between 0.5 mm and 2.5 mm), before being used as raw material in the brick manufacturing process.
Scenario 4 considers the production of heat (current scenario) from 100 percent WW (S4-100 percent WW), with the same proportions of GA and GB, and then compares the result to the heat produced with 100 percent virgin wood (S4-100 percent NW), accounting for the maximum emissions parameters established in CONSEMA Resolution 370/2017 on the use of uncontaminated MDF and MDP as a fuel source.
This legislation aims to limit emissions of formaldehyde and volatile organic compounds that are highly harmful to human health.
The resolution comes from the state of Rio Grande do Sul and was adopted in this study because the state of Espírito Santo does not yet have specific legislation on the subject. Thus, the results obtained are compared within the context of the controlled burning established in this legislation.
WW from the furniture industries in Linhares and Colatina is transported to the brick factories in Colatina and São Roque do Canaã. The reference flow is the production of one kg of ceramic. After the electric chipper stage, the waste is sent to the kilns as fuel for heat production.
The foreground inventory was drawn up based on Vinhal. The data on air emissions were sourced from IBAMA reports, the maximum limits established by CONSEMA resolution 370/2017 and Vinhal.
Biogenic CO2 emissions from burning wood in the kilns were considered to be neutral.
In this study, regarding brick manufacturing, importantly, although the analysis was carried out separately for Scenarios 3 and 4, the use of waste occurred jointly in both the production and heating processes.
Therefore, to avoid competition between the two applications, we believe that GB waste has great potential for inclusion in bricks. However, the behaviour of this type of waste from MDF and MDP panels in bricks exposed to temperatures above 750 deg C requires further investigation in terms of the resulting emissions.
Scenario 5
Scenario 5 considers the disposal of WW in a landfill, including transportation from the furniture industry to the landfill—an average distance of 30 km for the furniture industries in Colatina and Linhares.
The reference flow is the disposal of one kg of waste. In this scenario, WW is collected by trucks and taken to landfills in Colatina and Linhares. The waste is then disposed of and sent for treatment. The Ecoinvent database version 3.6 was used for the LCI.
Life-Cycle Impact Assessment & Interpretation
The software used for the LCA was OpenLCA version 1.10 with the Ecoinvent database version 3.6 cutoff for the background inventory.
The methodologies used for the LCA were IPCC 2013 (100 years), CML baseline, and USEtox for human toxicity. The six most studied environmental categories for WW management systems, as identified in the literature review carried out by Pinho and Calmon, were adopted for this analysis.
This group includes global warming (GW), acidification potential (AC), eutrophication potential (EU), ozone depletion (OD), human toxicity–non-cancer (HT-NC), and human toxicity–cancer (HT-C).
The furniture industries in the state of Espírito Santo are mainly located in Colatina, Linhares, and Gran Vitória. As this research focuses on the furniture hubs of Linhares and Colatina, through sensitivity analysis, we sought to answer the following question: is it feasible to take the WW of the furniture factories in Gran Vitória to Pinheiros (panel factory) or to Colatina and São Roque do Canaã (ceramics factories)?
The feasibility of transportation distances for the use of furniture WW generated in the Gran Vitória region was therefore investigated in the proposed scenarios. A point located in the north and another in the south of the metropolitan region of Gran Vitória were considered to study the feasibility of acquiring WW.
As part of the region analysed is covered by a railway line, two analyses were carried out for each extreme point: one with the train associated with the cargo truck, and the other with just the truck as the means of transport.
However, this analysis did not incorporate the loading and unloading operations for the integration of the train and the truck, which may require energy and material consumption for conveyor belts, wagon turners, and lifting platforms, among others.
The reference flow of one tonne of WW collected from the furniture industry in Espírito Santo and managed was used to compare the scenarios evaluated.
This comparative analysis was based on the environmental benefit obtained from using WW to produce MDF, MDP, ceramic bricks, and heat for pottery. Therefore, the first four scenarios were also calculated using only virgin sources, and the difference in impacts was the environmental benefit.
Results Comparison
Although the environmental impacts of manufacturing reconstituted panels (MDF and MDP) and ceramic bricks can be influenced, for example, by differences in technology, fleet characteristics and transportation distances, or percentage of resin, it was possible to verify that the results obtained were consistent with the literature consulted.
The MDF studied in Scenario 1 used a higher percentage (14 percent and 13.5 percent w/w) of resin in its composition than that in the study by Piekarski et al., which used 10.3 percent w/w; this material is a relevant factor in the increase in emissions observed in the panels.
Silva et al. conducted a cradle-to-grave study in Brazil, but heavy fuel oil was the main boiler fuel, which contributed to a higher GW value.
The replacement of heavy fuel oil with more environmentally friendly inputs in industrial production can result in better environmental performance of the MDP. The analysis of MDP in Scenario 2 adopted WW as the boiler fuel, which led to better environmental performance of the product.
Vinhal carried out two studies in Brazilian ceramic brick factories that also used WW as fuel for the kilns, but the transportation distance of some raw materials was close to the ceramic factories, in contrast to the distances in this study. For example, clay, which is the main raw material, is extracted an average of 40 km from the factories studied.
In the analysis by Vinhal, this distance was not accounted for. In both studies carried out by the author, the clay extraction process was carried out by the ceramics industry itself.
Comparative Analysis
With regard to Scenario 4, which considers the production of heat in the ceramics industry (current practice), the benefits by category over time are closer to those of Scenario 2 (MDP) but are still lower.
Only in relation to Scenario 3 does the environmental benefit of Scenario 4 show a greater advantage in all of the categories evaluated.
MDF (Scenario 1) stands out as having the highest environmental benefit values for GW. It also indicates that for one tonne of waste, the disposal scenarios for MDP (Scenario 2), brick (Scenario 3), and heat production (Scenario 5) show environmental benefits of between 20 and 40 kg CO2 eq.
However, when analysing annual production, the figures show greater advantages for MDF and MDP in relation to brick production and energy production.
In addition, in the research by Buschalsky and Mai, MDF was recovered up to the third generation of panels by using the thermohydrolytic disintegration process; furthermore, Kim and Song stated that MDP can be recycled up to 16 times after use, which demonstrates the potential circularity of these products prior to being sent to landfills or incinerated.
Scenario 3 shows that the inclusion of 1 tonne of waste as a raw material in the manufacturing of bricks, compared to those produced with 100 percent clay, resulted in a reduction of 29.0 kg CO2 eq. Considering that a brick masonry wall can remain in a building for more than 40 years, the carbon storage time before recycling or final disposal would also be 40 years.
In Scenario 4, energy production (heat) in the brick factory was evaluated using one tonne of WW as a burning fuel, replacing virgin eucalyptus. A reduction of 37.5 kg CO2 eq was found.
This scenario (reference) is the usual waste disposal practice adopted by the furniture industry. However, in the analysis carried out considering the annual production of the region’s ceramics industry, the environmental gains were smaller when compared to those of Scenarios 1 and 2.
In Scenario 5, emissions from the disposal of WW in landfills were associated with 83.74 kg of CO2 eq per GW for managing one tonne of WW. The emissions from this landfill were calculated using the Ecoinvent database version 3.6, which considers only WW from natural wood.
The inventory used was ‘treatment of waste wood, untreated, sanitary landfill/waste wood, untreated/cutoff, U’. It was therefore not possible to account for emissions from components of MDF and MDP waste, such as those resulting from UF resin. This indicates that the environmental burden may be greater.
In view of the above, Scenarios 1 and 2 are potentially more favourable for waste disposal compared to Scenario 4. Scenario 3 has a lower environmental gain compared to Scenario 4, but could be a promising alternative for disposing of GB waste.
Scenario 1 appears to be the best option, and its environmental benefit for managing 1 tonne of waste exceeds the second option by 60 percent (heat) in relation to GW.
Considering the amount of waste needed to meet the monthly production of the projected scenarios and the estimated monthly generation of WW (6,700 tonnes) in the Colatina and Linhares furniture hubs, more than one scenario could be used.
For example, Scenario 1 could be considered together with Scenario 4. However, the quantity of WW is sensitive to market demand. In addition, correct sorting is crucial for the best use.
Therefore, the creation of data-sharing platforms between industries, with information on sorting and the amount of waste available to support supply and demand planning, is an important factor in the development of a CE in the region studied.
Sensitivity Analysis
The sensitivity analysis in relation to transportation distances for the three products studied: MDF, MDP, and ceramic bricks shows that for each base case (i.e., product with virgin source inputs), purchasing WW is viable throughout Gran Vitória.
Importantly, the point located in the south of GV for Scenario 3 (ceramic bricks) exceeds the base case. However, the option that integrates the train with a freight truck shows a significant reduction.
The destination of GV waste for the manufacturing of bricks proved to be more attractive with the use of transport that integrates trains and trucks, because the red ceramics factories are close (28 km) to the Colatina train station. As a result, the journey to the ceramics factories by freight truck was shorter than for MDF and MDP.
Within the context analysed, integration of the train and freight truck for completing the necessary journeys achieved lower emissions for the three products at the two points analysed in the GW category.
Conclusions
In this study, a comparative LCA was carried out to evaluate the environmental performance of different scenarios for the disposal of WW generated by the furniture industry of Espirito Santo, with the central-northern area of the state as the spatial focus of the research.
To assess the environmental impacts, five WW management scenarios were studied: MDF production, MDP production, solid ceramic brick production, heat production in the ceramics industry (current practice), and landfill disposal.
The results showed that Scenario 1 (MDF) achieved more environmental benefits in all of the evaluated impact categories compared to the base scenario without using waste materials.
The categories studied included GW, AC, EU, OD, HT-NC, and HT-C. Notably, one cubic metre of MDF stores 1080 kg CO2 eq/cubic metre, which results in a net impact of −849 kg CO2 eq/cubic metre of MDF.
In relation to MDP, one cubic metre of the studied panel stores 1174 kg CO2 eq/cubic metre, resulting in a net impact of −975 kg CO2 eq/cubic metre of MDP.
Scenario 5 (landfill disposal) is the least favourable practice, and its emissions are associated with 83 kg of CO2 eq in the GW category for one tonne of WW.
With regard to Scenario 4 (current practice), only when compared to Scenario 3 (ceramic bricks) is its environmental benefit greater in all of the evaluated categories.
It is, therefore, possible to see that Scenarios 1 and 2 are potentially more favourable for disposing of WW than Scenarios 3 and 4. Scenario 3 has a lower environmental gain compared to the other scenarios but could be a promising alternative for disposing of wood panel waste (Grade B).
With regard to panels, notably, the literature highlights the potential circularity of these products before they are sent to landfills or incinerated. For example, MDP can be recycled up to 16 times after use.
The results of the sensitivity analysis in relation to transportation distances support the environmental viability of purchasing WW from companies in Gran Vitória to manufacture the studied products. However, Scenarios 3 and 4 show the greatest benefits, especially when rail use is included in the journey.
Based on quality, WW from the furniture industry can be used in different scenarios, thus avoiding competition between them. However, most of the furniture companies surveyed do not separate their waste carefully, which is a limiting factor for using it in new cycles that add value to the waste.
The creation of platforms for sharing data between industries is also necessary; these should include information on the classification and quantity of waste available to support supply and demand planning.
In addition, the government must promote and strengthen policies that encourage and promote solid foundations for the development of the CE.
This study sought to provide a broad overview of different alternatives for reducing environmental impacts, while presenting efficient and possible solutions for managing WW. The scenarios were constructed by detecting existing synergies and bringing local industries together, with the aim of building a network of value for stakeholders.
Finally, it is hoped that the analyses carried out in this research will be of interest to industries in the area, entities linked to the furniture sector, and public policymakers, as these bodies can help in the decision-making processes on WW management, especially at a regional scale, as addressed in this research.
The scenarios in this study describe possible ways to use WW as a raw material for manufacturing new products, thus reducing the demand for virgin sources and increasing environmental gains.
