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Environmental impacts of wooden, plastic, and wood-polymer composite pallet: a life cycle assessment approach

Descripción: Environmental impacts of wooden, plastic, and wood-polymer composite pallet: a life cycle assessment approach Waste recycling is one of the essential tools for the European Union's transition towards a circular economy. One of the possibilities for recycling wood and plastic waste is to utilise it to produce composite product. This study analyses the environmental impacts of producing composite pallets made of wood and plastic waste from construction and demolition activities in Finland. It also compares these impacts with conventional wooden and plastic pallets made of virgin materials. Methods Two different life cycle assessment methods were used: attributional life cycle assessment and consequential life cycle assessment. In both of the life cycle assessment studies, 1000 trips were considered as the functional unit. Furthermore, end-of-life allocation formula such as 0:100 with a credit system had been used in this study. This study also used sensitivity analysis and normalisation calculation to determine the best performing pallet. Result and discussion In the attributional cradle-to-grave life cycle assessment, wood-polymer composite pallets had the lowest environmental impact in abiotic depletion potential (fossil), acidification potential, eutrophication potential, global warming potential (including biogenic carbon), global warming potential (including biogenic carbon) with indirect land-use change, and ozone depletion potential. In contrast, wooden pallets showed the lowest impact on global warming potential (excluding biogenic carbon). In the consequential life cycle assessment, wood-polymer composite pallets showed the best environmental impact in all impact categories. In both attributional and consequential life cycle assessments, plastic pallet had the maximum impact. The sensitivity analysis and normalisation calculation showed that wood-polymer composite pallets can be a better choice over plastic and wooden pallet. Conclusions The overall results of the pallets depends on the methodological approach of the LCA. However, it can be concluded that the wood-polymer composite pallet can be a better choice over the plastic pallet and, in most cases, over the wooden pallet. This study will be of use to the pallet industry and relevant stakeholders. Pallets are used for storing, protecting, and transporting freight. They are the most common base for handling and moving the unit load, carried by materials handling units, such as forklifts. The pallet market is growing due to the rising standard of goods transportation, the adoption of modern material handling units in different industries, and market demand for palletised goods (McCrea 2016). It was estimated that the global pallet market reached 6.87 billion units in 2018 (Nichols 2020). More than 600 million European Pallets Association (EPAL) approved pallets are available to the global logistics industry. In 2019, 123 million wooden EPAL pallets and other carriers were produced, which is 1.2 million more compared to 2018 (EPAL 2020). The global pallet market can be classified based on materials, sizes, and management strategies (Deviatkin et al. 2019). Among various segments of pallets, wooden pallets dominate the market share, followed by plastic pallets (Leblanc 2020). Wooden pallets are inexpensive and can easily be manufactured and repaired compared to rackable plastic pallets. One of the most significant downsides of wooden pallets is the cost to forests (Retallack 2019). Furthermore, wooden pallets are heavier than plastic pallets, imposing an environmental burden on freight shipment. Even though plastic pallets are lighter than wooden pallets, plastic pallets' production is an energy-intensive process. In addition, repairing plastic pallets is impossible because the materials have to be melted down and remoulded in the plastic pallet repairing process. Waste recycling is one of the pathways taken by the European Union to move towards a circular economy, as highlighted in the circular economy action plan (European Commission 2020). The central idea of a circular economy is to minimise the consumption of virgin materials, which means that an item that can be recycled should not be landfilled or incinerated. The EU is planning to recycle 50% plastic and 25% wood waste by 2025, which will increase to 55% for plastic and 30% for wood by 2030 (European Commission, 2018). By following the EU's target, Finland's objective is to fortify its role as a pioneer in the circular economy by implementing the strategic programme for circular economy (Ministry of Employment and the Economy 2021). The transition to a circular economy is essential for Finland to strengthen its export-driven economy with minimum environmental impact. The environmental benefits of recycled-based plastic products are well known and quantifiable (WRAP 2019). Also, materials made from wood waste can deliver low carbon-based products with less pressure on forests (WWF 2016). One of the possibilities for reducing the environmental burden of plastic and wood waste is to utilise these wastes for wood-polymer composite (WPC) products, such as WPC pallets. However, analysing the environmental performance of WPC pallets requires a complete life cycle analysis. Furthermore, it is important to consider that different materials have different life expectancies, reuse capabilities, and recyclability. According to International Organization for Standardization (ISO), life cycle assessment (LCA) is one of the environmental management techniques that "addresses the environmental aspects and potential environmental impacts throughout a product's life cycle from raw material acquisition through production, use, end-of-life treatment, recycling, and final disposal" (EN ISO 14040:2006; EN ISO 14044:2006). Several LCA studies have been conducted on pallets focusing on pallet manufacturing, management strategies and supply chains, repair intensity, and pallets manufactured from various materials, such as wood, virgin plastic, cardboard, and waste plastic. Gasol et al. (2008) conducted an LCA study to compare the environmental performance of wooden pallets with high reuse intensity and low reuse intensity in the European context, and with the findings showing that due to transportation, high reuse intensity pallets have more adverse impacts on climate change than low reuse intensity pallets. Bengtsson and Logie (2015) performed an LCA comparing one-way wooden pallets, disposable compressed cardboard pallets, pooled softwood pallets, and plastic stackable pallets in Australia and China. The study results pointed out that pooled softwood pallets have the minimum environmental impact among all types of studied pallets. Tornese et al. (2018) examined pallets' economic and climate change impacts, demonstrating that manufacturing a pallet causes more damage to the environment than repairing a pallet. The study also identified that the cross-docking system has equivalent emissions as the take-back system due to higher transportation distance. Almeida and Bengtsson (2017) compared the LCA of waste plastic-based pallets with wooden pallets and virgin plastic-based pallets and demonstrated that plastic waste-derived pallets outperform all other alternatives. Franklin Associates (2007) compared the environmental impacts of pooled pallets versus non-pooled pallets. The study indicated that pooled pallets have less of an environmental burden than non-pooled pallets. Ko?í (2019) studied the environmental impact of wooden pallets, primary plastic pallets, and secondary plastic pallets. The study found that wooden pallets have a better environmental impact than primary and secondary plastic pallets if energy recovery occurs. Furthermore, the study also showed that the weight of the pallet plays a significant role on its total environmental impact. The authors of previously conducted LCA studies analysed various pallets, making their cross-comparison a difficult task. Previous literature, including the above mentioned studies, have conducted LCA from an attributional point of view and excluded consequential LCA, which is thought to be an important method for identifying the changes in the system as a consequence of using a particular pallet. It is important to investigate the differences in the results, conclusions, and suitability of attributional and consequential LCA for cases where waste recycling is included. Furthermore, all the former studies assumed that various pallets perform equally well during their life cycle. None of the studies considered that pallets made with different materials have different life expectancies, repairing times, and recycling rates. In addition, end-of-life (EoL) is an integral part of the cradle to grave LCA. The methodological difference of the EoL allocation might have a significant impact on the overall result of LCA. It is found that the allocation of the environmental burdens of the EoL of the pallets was absent in the studies as mentioned earlier. The goal of this LCA study was to calculate and assess the environmental impacts of manufacturing, utilising, and disposal of pallets made of different materials. Both attributional LCA (ALCA) and consequential LCA (CLCA) methods were used in the study. An ALCA investigates the environmental impact of the physical flows to and from a product's life cycle and its subsystems (Ekvall et al. 2016). In contrast, consequential LCA investigates the environmental impacts of the product system and the systems linked to it that are expected to change for production, consumption, and disposal of the product (Ekvall et al. 2016). Despite the ISO 14040/44 standards not explicitly distinguishing between the two types of LCAs, there is a clear difference in the definition of the scope for those assessments, as described below. The study results are intended to guide the selection of materials for the production of pallets. Scope of the ALCA study The attributional LCA follows the cradle-to-grave approach, meaning that the product system includes the processes starting with the provision of raw materials from the environment in the form of elementary flows, i.e. the flows created by nature, through the use of the pallets and ending with their disposal and with the release of emissions into air and water, and to the generation of waste. The system boundary of the ALCA comparing the impacts of the pallet's production, use, and EoL is shown in Fig. 1. The modelling started with producing the raw materials and the energy generation for the pallets, such as wood harvest, timber production, and plastic production. It should be noted that the system boundary for WPC starteds from the collection of waste. Once the materials are produced and delivered to the production facilities, the pallets are manufactured. Nails are used to secure the parts of the wooden pallets, whereas plastic and WPC pallets are compressed into the required shape and do not require any fixing elements. The pallets are then delivered to a pallet pooling company, which operates by delivering the produced pallets to customers who can use them for their own purposes. After which, the pooling company collects the pallets and repairs them in the case of wooden pallets, if needed. After being used, the pallets are crushed for incineration. In the case of wooden pallets, ferrous metals are separated before incineration. By incinerating wooden, plastic and WPC pallets' waste, energy is substituted. Nevertheless, materials are also substituted by separated ferrous metals from wooden pallets. EoL allocation There are no strict or specific requirements for modelling the EoL in LCA, and several allocation methods exist, such as 0:100 approach, 100:0 approach, 100:100 approach, 50:50 approach, etc. (Allacker et al. 2017). 0:100 EoL method can be conducted in two different ways, such as 0:100 with no credit for avoiding virgin materials and 0:100 with credit for avoiding virgin materials (Allacker et al. 2017). The system boundary of the study ends at the recovery of energy and material from the EoL phase. Therefore, in this study, the 0:100 EoL method with credit system had been used. In the CLCA, the correct way of modelling environmental impact is to use marginal production technology data for the substituted product. Marginal production technologies are those technologies that are changed by the small changes in demand (Weidema et al. 1999). It was found from this study that a significant amount of heat and electricity substitution was impacted when wood and plastic waste were not incinerated but used for WPC pallet production. In this case, marginal heat and electricity were used in the modelling of CLCA. Biomass will be the prime heat production source in Finland by 2030 (Ministry of Employment and the Economy 2017), and wind and solar power will provide the maximum share of electricity by 2030 (SKM Market Predictor 2019). Therefore, the biomass-based heat source was selected as the marginal heat source and wind, and solar-power-sourced electricity was selected as the marginal electricity source in CLCA modelling. The more detailed information on the selection of marginal heat and electricity is presented in the supplementary materials. Selection of the pallets A great variety of pallets exists, as dictated by the specific requirements of customers. However, this study exclusively focused on pooled pallets, with the dimension of 1200 mm?×?800 mm, made of either wood, plastic, or WPC. The pallets with the above-specified dimension are widely known as EUR pallets and are the most widely used type of pallets in Europe (EPAL 2019). Table 1 specifies the key parameters of the studied pallets in their baseline scenario. Wooden pallets are made of virgin wood, which is a mixture of softwood and hardwood as specific to Finnish conditions. The studied wooden pallets were block-type pallets, which are commonly used in Europe. Based on the review of LCA studies of wooden and lightweight plastic pallet by Deviatkin et al. (2019), the expected lifetime of the wooden pallets is 20 cycles, yet the number ranged between 5 and 30 cycles in most of the publications reviewed. The repair need of 7 cycles was estimated based on the mass of produced EUR pallets in Finland (3.2?×?103 kg), alongside with repaired (25?×?103 kg) and reused (167?×?103 kg). The expert views from a Finnish pallet pooling company suggested that the expected lifetime of the wooden pallets is somewhat higher, whereas the repair need for the pallets occurs on average after every 12 cycles. The variations in the expected lifetime of the pallets were examined in the scenario analysis of this study. It was assumed that, at the EoL, 90% of wooden pallets are incinerated, whereas 10% are used as a bulking agent in composting facilities. The plastic and WPC pallets are identical in structure and production method. Plastic pallets are manufactured using injection moulding, whereas WPC pallets are produced by extrusion followed by a compression moulding process. Both pallets are made to allow their nesting, thus saving the space occupied by the pallets. The exact height occupied by wooden stackable pallets can fit 1.7 times more plastic or WPC pallets. According to the literature on plastic pallets, plastic pallets are more durable than wooden pallets (Deviatkin et al. 2019). The expected lifetime of Double Sided Plastic Pallets could be 66 cycles, whereas the lifetime ranges from 50–100 in most of the studies reviewed (Deviatkin et al. 2019). In this study, the lifetime of plastic pallets was considered to be 66 cycles by following the review study conducted by Deviatkin et al. (2019). The WPC pallets were assumed to be of comparable properties as plastic pallets in these terms. Plastic and WPC pallets are suitable for demanding applications, such as those with expected exposure to water, or specific industrial demands, like those of the pharmaceutical industry. Such features of plastic and WPC pallets are, however, not considered in this study. Once damaged, neither plastic nor WPC pallets can be repaired.

Fecha de Publicación: 15-10-21

The Science of LED Grow Lights for Your Indoor Garden

Descripción: The Science of LED Grow Lights for Your Indoor Garden Indoor Gardening isn't exactly a new thing, but LED's are changing the way we light our indoor gardens.  LED lights are more efficient than traditional fluorescent and incandescent lights.  That's because LED lights convert nearly all of their energy (95%) into light, while other lights turn a significant amount of energy into heat.  But, there's another very important reason that LED's are more efficient when it comes to growing plants.  With LED lights, we have the rather unique ability to customize the type of light that is emitted, and that means we're not wasting energy to create light that doesn't help our plants grow.  At the end of this article, you'll understand the science behind why spyder grow light series come in many different colors, as well as why some LED grow lights cost so much more than others.  Plants Only Use the Visible Light Spectrum for Photosynthesis It's important to know that plants only use visible light (the colors of light that we see every day) for photosynthesis. However, as the chart below demonstrates, the complete spectrum of light is far greater than just the visible light spectrum.  On the outer edge of the visible light spectrum is Ultraviolet (UV) light and Infrared Radiation (IR).  UV light is the invisible light emitted by the sun and other sources that will cause sunburns when we don't wear sunblock.  IR light can only be seen with special equipment, like night-vision goggles.  Even further out from the visible light spectrum are light waves that we don't traditionally think of as light.  These include X rays, Microwaves and even Radio Waves. One of the most important things to understand is that scientists have demonstrated over and over again that plants only absorb visible light for photosynthesis.  Plants do react to other forms of light like UV, but that reaction is typically negative.  I'm told that marijuana growers actually use UV light to induce the production of psychoactive chemicals like THC, which seem to be produced in part as a defense mechanism against the damaging effects of UV light to the plant. What is PAR? PAR stands for "photosynthetically available radiation."  PAR is made up only of visible light, because this is the only light that plants use for photosynthesis. For decades, many indoor growers have used Lumens to measure a grow light's efficacy, but the industry is getting smarter and turning to PAR.  Lumens are used to measure the brightness of a lamp to the human eye.  But plants and people see light differently.  Humans see yellow and green more brightly than other colors.  Therefore, yellow and green lamps may have higher Lumen values than red and blue lights that put out just as much actual light, and which plants are likely to respond better to. PAR measures all light from the visible light spectrum equally, and does not measure light outside of the visible light spectrum, which does not help the plant photosynthesis.  So, for plants, the PAR value of a light is currently the best basic measurement of a grow light's brightness.  Accurate PAR meters are quite expensive and generally cost $500 or more.  Inaccurate PAR meters can be purchased for much less, but there's really no point to owning an inaccurate PAR meter.  The best way to get PAR values for your 400W LED grow light, assuming you don't want to purchase your own PAR meter, is to check with your reputable grow light manufacturer or provider for the PAR rating of their lights.  How Much PAR do My Plants Need to Grow? The amount of PAR your plants require depends on what you are growing, as well as how far away from your plants the light is.  Generally speaking, leafy greens like lettuce only need a PAR value of ~200, whereas tomatoes and other plants that flower and produce fruit require 400-500 or more PAR.  Unless you place your 600W LED grow light right on top of your produce, you will need an even higher PAR rating from your grow light, to take into account the distance between your plant and the light source. In the example below, you can see a very powerful grow light that puts out nearly 1,900 PAR (measured in umol) 8 inches from the source.  Very few lights put out this much PAR, and they are typically quite expensive.  This light will emit 1,900 umol every second.  But at 23 inches from the source, the strength of the light is reduced to 890 umol.  The PAR value is reduced further and further as you get further from the light source.  When we get to 6 feet away from the light source, our PAR value is down to ~100umol, which means we would have trouble growing even lettuce well.  So, always make sure you understand not just the PAR emitted from the light, but that every 8 inches or so away from your light, the PAR value will be reduced by ? or more. There are many inexpensive grow lights on the market that make big claims, but they will ultimately leave their owners disappointed.  This issue is especially rampant on the internet.  Remember to check the PAR value of any light you purchase.  Also, remember to take into account how far your light will be from your plant to ensure there is enough photosynthetically available radiation (PAR) for your plant to flourish. Leafy Greens require 200 PAR for proper growth Tomatoes, cucumbers and other flowering/fruiting vegetables require 400-500 PAR Fruiting Trees should be given 600 PAR or more What is the Temperature of Light I Should Use? Interestingly, 'Kelvin temperature' is the metric used to describe the visual color that a light emits.  As you can see in the chart below, 'warmer' light temperatures that have a red color have a lower Kelvin rating.  On the other end of the spectrum are 'cooler' temperature lights which have a blue color and higher Kelvin rating. Different temperatures of light have different impacts on plants.  Generally, higher temperatures (blue) light encourages photosynthesis which leads to bushy plants that don't feel inclined to elongate and reach for more light.  This is great if you want to grow in a compact space.  Lower temperature (red) light reduces photosynthesis and signals to plants that that it's time to flower and produce fruit.  Plants put under a red light will also be more inclined to stretch and grow taller, as opposed to growing bushier and more compact. IGWorks focusses on providing full spectrum lights with a natural color temperature of between 4500K-6500K as these are most pleasing to the eye.  They also allow plants to grow bushy and compact, without hindering the ability of plants to flower and fruit.  What Color of Light Should I Use? LED lights can come in almost any color.  Plants respond most to red and blue light.  Interestingly, plants generally respond less well to green light.  In fact, the reason that plants appear to be green is that they tend to reflect green light, while they absorb other parts of the light spectrum more readily.  This is why a large scale or industrial grower of plants will often use a combination of red and blue lights to photosynthesize their plants.  They don't want to waste electricity producing green and even yellow light, which plants use less effectively.  However, for those of us growing produce in our living spaces, it's probably worth the extra pennies it costs to produce a nice full-spectrum color that will be more natural and pleasing to the eyes.  Full-spectrum grow lights will often come with a chart, which shows the distribution of blue, green, yellow and red light that is emitted.  See the example below Choosing the right grow light spectrum for your commercial operation can be a challenge. Many 800W LED grow light suppliers have conflicting information on the topic due to bad marketing or simply a lack of knowledge in plant and light research. In this article, our light spectrum experts break down what light spectrum is, how plants respond to light, and how light spectrum influences plant growth. What is Grow Light Spectrum? Light spectrum is the range of wavelengths produced by a light source. When discussing light spectrum, the term 'light' refers to the visible wavelengths of the electromagnetic spectrum that humans can see from 380–740 nanometers (nm). Ultraviolet (100–400 nm), far-red (700–850 nm), and infra-red (700–106 nm) wavelengths are referred to as radiation. As growers, we're most interested in the wavelengths that are relevant to plants.  Plants detect wavelengths that include ultraviolet radiation (260–380 nm) and the visible portion of the spectrum (380–740 nm) which includes PAR (400–700 nm), and far-red radiation (700–850 nm). When considering light spectrum for horticultural applications, greenhouse and indoor environments will differ.  With indoor environments your grow light's spectrum will account for the total light spectrum that your crop receives.  Whereas in a greenhouse you must consider that your plants are receiving a combination of folding grow light series and solar spectrum. Either way, the amount of each waveband that your crop receives will have significant effects on growth.  Let's learn more about how this works. Plants use light for photosynthesis and photomorphogenesis. Photosynthesis is the process by which plants and other organisms convert light energy into chemical energy. Photomorphogenesis refers to how plants modify their growth in response to light spectrum. One example of photomorphogenesis is a plant bending toward a light source. Light also affects plants' developmental stages, such as germination and flowering. The light that plants predominately use for photosynthesis ranges from 400–700 nm. This range is referred to as Photosynthetically Active Radiation (PAR) and includes red, blue and green wavebands. Photomorphogenesis occurs in a wider range from approximately 260–780 nm and includes UV and far-red radiation. Although results are dependent on other factors, there are general rules of thumb that you can follow when using light spectrum to elicit different plant responses. Outlined below is an overview of how each waveband is used for horticultural purposes so that you can trial light spectrum strategies in your own growth environment and with your chosen crop varieties. Blue light has distinct effects on plant growth and flowering. In general, blue light can increase overall plant quality in many leafy green and ornamental crops. A minimal amount of blue light is required to sustain normal plant development.  In terms of adjustable spectrum lighting strategies, if we were to equate red light to the engine of your car, then blue light would be the steering wheel. When combined with other light spectrum wavebands, blue light promotes plant compactness, root development, and the production of secondary metabolites.   Blue light can be utilized  as a growth regulator, which can reduce your need for chemical plant growth regulators (PGRs). Blue light can also increase chlorophyll accumulation and stomatal opening (facilitating gas exchange), which can improve overall plant health. One example of blue light influencing secondary plant metabolite production is how blue wavebands promote anthocyanin development in leaves and flowers. Increased anthocyanin levels result in more pronounced color. Blue light also promotes other secondary metabolic compounds associated with improved flavor, aroma and taste. For example, blue light treatments have been shown to improve terpene retention in some varieties of cannabis. Higher intensities of blue light (>30 μmol·m-2·s-1) can inhibit or promote flowering in daylength-sensitive crops. Blue light does not regulate flowering at low light intensities (

Fecha de Publicación: 15-10-21

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