Assessing Green Features of “Phumdi” as a Sustainable Material: A Comparative Analysis with Bamboo, Wood, Metal, and Plastic

Abstract

Sustainable materials and their potential application in building industries are gaining attention; however, there is still largely unexplored floating biomass, notably “Phumdi”, as a sustainable floating building material. Phumdi, a distinctive floating biomass, is observed in specific wetland habitats in the Loktak Lake located in Manipur, India. This heterogeneous mass of vegetation, organic matter, and soil has been utilised by several communities for various purposes, such as medicine, food, forage, and material for building houses, handicrafts, and aquaculture activities. Such floating bodies serve as a sanctuary for a wide range of flora and fauna. The study aims to conduct a comprehensive comparative analysis of phumdi as a sustainable floating material in comparison with other widely recognized construction materials such as recycled plastics, bamboo, corrugated metal sheets, and wood by evaluating the “green feature” chart. The research and experiments carried out on phumdi have underscored the highest sustainability level for its use, i.e., 15 green features, followed by wood and bamboo with 14 features, and the other two materials with low sustainability performance: plastic barrels with seven features and corrugated zinc metal sheets with eight features. Further investigation is necessary for the advancement of this material as a viable alternative for biomass-based building materials.

1. Introduction

An unusual floating mat of plants is found in Loktak Lake, located in Manipur, north-east India (see Figure 1a). ‘Phumdi’ is the native name for a floating biomass made of a substantial quantity of soil, plant life, and organic materials in various stages of decomposition, which has naturally undergone thickening over time [1]. The presence of this heterogeneous mass of plants contributes to the unique characteristics of the lake ecosystem. The ability of phumdi to remain afloat is attributed to its low specific gravity and high buoyancy, which are consequences of the substantial quantity of vegetative matter it encompasses. Approximately 20% of the overall thickness of the phumdi is observed to be buoyant above the water surface of the lake, with the remaining 80% being submerged [2]. They exhibit a variety of thicknesses and dimensions, spanning nearly half of the water surface area of Loktak Lake, which is approximately 287 sq. km [3].

Phumdi plays a crucial role in the ecosystem processes and functions within the Loktak Lake environment, in addition to their significant social and economic value for local people. It is utilised as a fishing platform, a floating foundation for houses, and a source of several plants that are utilised for food, fodder, fuel, medicine, etc. Artificial floating islands, see Figure 1b, have been developed for purposes beyond fisheries and human settlement, including the enhancement of water quality, the provision of nesting platforms for wild birds, and the establishment of habitats for aquatic animals [4,5]. The Athaphum, an innovative buoyant pond constructed by indigenous peoples, incorporates phumdi as a fundamental design component for the specific objective of fishing, as seen in Loktak Lake. The traditional fishing technique involves cutting the phumdi strips into particular sizes and attaching them in a circular pattern with a circumference of 200–250 m; see Figure 1b [6]. With the trends of contemporary design and construction, a focus on sustainable ways of thinking is much needed to bring in the lake. However, to proceed in this direction, a good understanding of flotation behaviour is needed, such as buoyancy and its design aspects.

The fishermen construct houses on floating Phumdi as a temporary shelter. This small hut serves as a short-term camp for the fishermen during the harvesting season, see Figure 1c. Usually, light, raw materials such as bamboo, wooden planks, and phumdi reeds are used to build the houses [1]. However, the existence of floating phumdi houses has increasingly been threatened by alternative building materials such as plastic barrels, corrugated iron sheets, and wood. Therefore, we argued that Phumdi and other buildings material in Loktak Lake need to be assessed from a sustainability perspective, especially in terms of material use. The increasing number of massive floating building projects has raised discussions on how environmentally friendly and feasible it is to replace materials, such as bamboo, wooden planks and phumdi reeds, in the long term. This research endeavours to compare phumdi with other well-established sustainable materials, such as recycled plastics, bamboo, corrugated metal sheets and wood, to highlight its comparative advantages and limitations.

Floating Building Materials Worldwide

There are several kinds of floating dwellings, each characterised by a unique construction technology and material usage. The material that is used in the similar types of floating communities that are located worldwide makes a connection between Loktak Lake and the material that is used. In the southern part of Peru, South America, Lake Titicaca is home to one of the most ancient floating villages globally, which has been inhabited by the Uros ethnic minority for several generations, see Figure 2a. The Uros community, which exists exclusively in the Titicaca Lake and is more than 500 years old, lives on buoyant foundations constructed from the roots of an aquatic flora known as Totora [7]. Totora reeds are the floating islands of the Uros in Lake Titicaca. The Uros people have developed customary techniques for building their dwellings, boats, and even the man-made islands where they live, with methods based almost exclusively on the totora culms [8,9]. In order to ensure the perpetuity of this floating island, a regular replacement of the reeds is conducted every three months, as the reeds at the bottom are rapidly decaying. The durability of this manufactured island extends for a period of up to three decades.

In the Southern District of Hong Kong, Aberdeen floating village is the most well-known floating village, see Figure 2b. The majority of those residing on boats in Aberdeen are Tanka. The Tanka ethnic group inhabits a group of primarily fishermen who arrived in Hong Kong between the 7th and 9th centuries [10]. Presently, the operations of villages have been intertwined with port activities, resulting in the coexistence of several communities inside these areas. The community is still using houseboats as their residences, with the older generations residing in cabins or relying on the river and sea banks, sowing timber piles, and constructing rafts. The top wall is made of bamboo, the floor mats are made of wooden slabs, and the dry fence building facing the water is a land-based residence that is convenient for working on the water [11].

In Cambodia, floating villages may be seen at Tonle Sap Lake and Rivers, which is the biggest freshwater lake in Southeast Asia, see Figure 2c. There are local fishermen living there. The prevailing belief is that the majority of the floating settlements in the Tonle Sap Lake region were created several centuries ago [12]. Buildings are simple, mostly bamboo frames and palm leaf panels. There are three distinct categories of dwellings that may be observed: ferry homes, traditional boat houses, and bamboo-structured houses. The floating of these structures is attributed to their construction on bamboo rafts, which are supplemented by buoyancy provided by metal barrels [13].

In certain regions of Vietnam, a number of floating communities can be found. The UNESCO World Heritage Site Ha Long Bay in Vietnam’s north-eastern seacoast is considered one of the world’s most attractive bays, see Figure 2d. This harbour is known for its floating fishing communities where people live together on the water [14]. There are two types of houses: stilt houses and barrel floating houses. Some floating houses are built on empty oil drums or pontoons as a means of buoyancy, while others are rafts that float on the water. The modest wooden post-and-beam floating dwellings were made of lightweight bamboo and wood. Plywood or planks were used for flooring, and the roofs were often bamboo-leaf thatching and coloured corrugated metal [15].

In this particular context, it is noteworthy that non-timber forest products, such as bulrushes, reeds, palms, herbaceous plants, and aquatic plants, are a significant source of biomass-based materials that can be investigated to diversify the range of biomass-based and low-energy construction materials. Numerous investigations have been undertaken to examine these particular plant species, assessing their viability for application in the building industry and their environment benefit [16,17,18,19].

Buildings often pose significant challenges to the achievement of environmental sustainability. The building and construction industry is the primary consumer of natural resources, including significant proportions of land utilization and material extraction [20]. Construction activities consume 50% of global raw materials, the majority of which are non-renewable resources. Furthermore, it contributes to the generation of 36% of the total waste generated globally [20]. In addition, one-third of global greenhouse gas (GHG) emissions are produced by buildings; this proportion rises dramatically as construction expands. The Intergovernmental Panel on Climate Change (IPCC) 2007 estimates that despite high-growth construction, building-related greenhouse gas emissions could nearly double by 2030, from 8.6 billion tonnes in 2004 to 15.6 billion tonnes [21]. The utilisation of materials that cause long-term environmental damage is one aspect of the building that poses a threat to sustainability.

Umar, Khamidi, and Tukur define sustainable building materials as those that are produced and sourced domestically, thereby minimising transportation costs and carbon dioxide emissions. These structures have the potential to be constructed using recycled materials, resulting in reduced environmental impact. Additionally, they exhibit enhanced thermal efficiency and require less energy compared to traditional building materials. Furthermore, they utilise renewable resources, resulting in less harmful emissions. Lastly, they provide economic viability [22,23].

A sustainable building material needs to be used appropriately and contextually in every community development. The utilisation of sustainable construction materials not only reduces transport costs, carbon emissions, and material expenditures but also provides community members with opportunities for employment and skill development [24]. According to Jin Kim Jong, the integration of sustainable materials is necessary at every stage of the material manufacturing process, from gathering raw materials to the subsequent distribution and installation, and ultimately, the eventual reuse or disposal of these materials [25]. It has been said that there are fifteen criteria that must be satisfied by sustainable materials, which are applicable across all stages of the building life cycle. Investigating natural fibers might lead to a more sustainable future for architecture through the use of a wider range of building materials, forms, and even the improvement of currently utilized materials [9]. In the present study, we aim to understand the potential of the Phumdi as a source of sustainable material that could be utilized in contemporary sustainable design construction. In the following, the materials and method to measure the green features of Phumdi are described.

2. Methods and Materials

The assessment of the sustainability of building materials was conducted using the ‘green features’ chart devised by Jin Kim Jong in 1998. The chart encompasses 15 distinct features that are categorised into three phases of the material’s life cycle: the pre-building phase, the building phase, and the post-building phase, see

Table 1. Green features charts of sustainable building material by Jin Kim Jong [26].

Pre-Building Phase	Building Phase	Post-Building Phase
Waste Reduction (WR)	Construction Waste Reduction (CWR)	Biodegradable (B)
Pollution Prevention (P2)	Energy Efficiency (EE)	Recyclable (R)
Recycled (RC)	Water Treatment and Conservation (WTC)	Reusable (RU)
Embodied Energy Reduction (EER)	Nontoxic (NT)	Others (O)
Natural Materials (NM)	Renewable Energy Source (RES)
	Longer Life (LL)

[26]. This chart facilitates the comparison of the sustainable qualities of different materials employed for a common purpose. The assurance of relative sustainability in a building material can be determined by the existence of one or more of the “green features” listed above in the material [25]. In order to measure the green feature of the Phumdi, the survey was conducted at Loktak Lake, Bishnupur district, Manipur, India. A comprehensive evaluation of the primary building material utilised by the many distinct types of floating structures in Loktak Lake was carried out, see Figure 3. The data collection for the research was gathered through direct field observation as well as interviews with communities during the months of June and October of 2023.

2.1. Pre-Building Phase

The Pre-Building Phase (Manufacturing Process) encompasses five distinct green features: (1) Waste Reduction (WR): material produced with the least amount of waste during the manufacturing process; (2) Pollution Prevention (P2): feature indicates that materials that produce the least amount of pollution; (3) Recycled Content (RC): featuring recycled element content in a material; (4) Reduction of Embodiment Energy (EER): required low total energy content in a material; and (5) Natural Materials (NM): The use of materials that contain natural ingredients and have lower toxicity.

2.2. Building Phase

The phase that involves the usage of materials and Building Operations is known as the Building Phase, There are six green features: (1) Reduction in Construction Waste (CWR): The utilisation of materials that possess efficient assembly procedures, hence lowering the amount of waste generated during building; (2) Energy Efficiency (EE): materials that have the potential for an overall reduction in energy consumption; (3) Water Treatment/Conservation (WTC): assembling materials that have no impact on the water quality and quantity surrounding the building site; (4) Non-Toxic (NT): Use of Less hazardous materials; (5) Renewable Energy System (RES)s: the materials that provide support for building systems based on natural energy sources. (6) Longer Life: material with long or durable lifetime. Material with a longer or more durable lifespan relative to other materials.

2.3. Post-Building Phase

The third stage, when the material passes through its lifetime and must be discarded, is the Post-Building Phase (Waste Management). There are four green features in the Waste Management (WM). (1) Biodegradability (B): The inherent capacity of a material to undergo natural decomposition and not be toxic when discarded; (2) Recyclable (R): The substance’s capacity for being transformed into new material through the process of recycling; (3) Reusable (RU): the material’s ability to be utilised in alternative builds; (4) Other capabilities (O) in any form that can contribute to a material’s sustainability performance.

3. Results

In Loktak Lake, it is observed that there exist three distinct categories of floating structures: (a) Phumdi house: building on floating phumdi with harvested phumdi reed, bamboo, and wood construction; (b) Poly barrel house: building on floating plastic barrels with a wooden structure and corrugated metal sheets; (c) Wooden stilt house: building with wooden structure and metal (see Figure 3). There are five main materials used by the buildings: (1) phumdi, (2) wood, (3) bamboo, (4) plastic barrels, and (5) corrugated metal sheet/rods. Here are the results of using the green features chart to evaluate the sustainability of each of the five materials.

3.1. Phumdi

Floating phumdi is used as the main construction material for its buoyancy and durability. It is easily available in Loktak Lake and is used in almost all building components, such as floating platforms, sub-structural frameworks, floorboards, walls, and roofs (see Figure 4). Some species from phumdi were used to create walls, such as Arundo donax, N. porphyrocoma, Phragamites karka, and Schoenoplectus lacustris, which gave the hut a light weight. Cymbopogon nardus, Erianthus arundinaceous, Imperata cylindrica, and Zizania latifolia are used to cover the rooftop. Overall, this material has a very high sustainability level because it has fifteen out of fifteen ‘green features’, see

Table 2. Green features of phumdi.

Pre-Building Phase	Building Phase	Post-Building Phase
WR	CWR	B
P2	EE	R
RC	WTC	RU
EER	NT	O
NM	RES
	LL

.

During the “Pre-Building Phase”, it is seen that phumdi possesses five out of the five currently available environmentally friendly characteristics. (WR+): During the process of harvesting raw materials and manufacturing, phumdi produces relatively little waste because the process is short and simple, and almost all the waste generated can be utilized for various purposes. Phumdi may be gathered without endangering the environment because it is readily accessible (PP+): The cutting and processing of phumdi are done manually or mechanically by the local fishermen, without much pollution. (RC+) Phumdi is a living material that is ‘renewable’; used phumdi can be grown again naturally; it has naturally recycled content. (EER+): Energy for phumdi processing is relatively small, as only physical effort is required for cutting. The distribution of phumdi is usually done by drifting logs along the surface of Loktak Lake. (NM+): The composition of phumdi consists entirely of naturally occurring materials. Despite the fact that phumdi can regenerate naturally, it can also be processed into other organic composts.

In the ‘Building Phase’, Phumdi has all six ‘green features’ that exist. (CWR+): Phumdi wastes assembled during construction can be converted into biomass soil compost or offer abundant nourishment for domesticated animals. (EE+): Phumdi assembly does not require much energy since it only required manual tools and labour. (WTC+): It is a floating biomass that requires water to float, and its purification also increases the quality of water around the lake. (NT+): Phumdi is a natural material that does not contain toxins. (RES+): Phumdi is a material that meets the passive cooling principle since it has low heat conductivity. (LL+): It comprises more than 120 plant species belonging to 46 families. Specific types of Phumdi species [1] have a very long life but need to change from time to time to continue growing.

In the ‘Post-Building phase’, Phumdi has all four “green features”. (B+): As a natural material, Phumdi can decompose naturally when disposed of in the soil. (RU+): Phumdi can be reused for various needs, as used phumdi plant can grow naturally again and form a fresh phumdi, and other dry phumdi reeds can be converted into walls, roof, and soil compost. (R+): Phumdi possesses the inherent ability to undergo natural regeneration, but it may also be subjected to processing methods with the purpose of transforming it into alternative forms of organic compost. (O+): Phumdi is categorized as a local material from Loktak Lake and is also renewable.

3.2. Wood

Stilt houses are constructed in close proximity to the shoreline of Loktak Lake. Wood is primarily used in the construction of wooden stilt houses because of its abundant accessibility and inherent durability. Timbers such as Teak, Pine, Oak, Uningthou (Phoebe spp.), and Leihao (Michelia spp.) are commonly used for a wide range of construction elements, encompassing foundations, stilt structures, structural frames, flooring, walls, and roof framing, see Figure 5. Overall, this material has a very high level of sustainability due to its fourteen ‘green features’, see

Table 3. Green features of wood.

Pre-Building Phase	Building Phase	Post-Building Phase
WR	CWR	B
P2	EE	R
--	WTC	RU
EER	NT	O
NM	RES
	LL

.

In the ‘Pre-Building Phase’, wood possesses four out of five existing “green features”. (WR+): Due to the brevity and simplicity of the harvesting and manufacturing processes, wood generates relatively little waste, and almost all the waste can be reused for other purposes. (PP+): Cutting and processing of wood are done manually or mechanically by industrial or timber companies with minimal environmental impact. (RC−): Wood is a renewable material that does not contain recycled content. (EER+): Energy for wood processing is relatively small, as only cutting is required. The distribution of timber usually requires less transport energy. (NM+): The material content in wood is one hundred percent natural substance.

In the ‘Building Phase’, wood has all six existing ‘green features’. (CWR+): Construction-related wood wastes can be reused for a variety of purposes. (EE+): The assemblage of wood requires little energy, since only a small proportion of devices require electrical energy. (WTC+): Wood processing and assembly during construction do not use an excessive amount of water so as not to impact the local water quality. (NT+): Wood is a natural substance that does not contain toxins. (RES+): Wood is a material that meets the passive cooling principle because it has low heat conductivity. (LL+): Specific types of wood species, such as “Uningthou” and “Teak”, have a very long life.

In the ‘Post-Building Phase’, wood has all four ‘green features’. (B+): As a natural substance, wood can naturally decompose when disposed of in the soil. (R+): Although timber is recyclable, flakes and wood powder can be processed into other materials. (RU+): Wood can be repurposed as new construction materials, furniture, and other products. (O+): Wood is categorised as a local material from hill forests that is close to Loktak Lake site and is also renewable.

3.3. Bamboo

Bamboo has been adopted as a feasible and sustainable construction material in several developing regions, such as Africa, South America, and the Far East, for an extended period of time. Extensive accessibility and rapid growth are observed in regions of China, Japan, and India [27]. In Manipur, it is broadly used in Loktak Lake, where it serves as a fundamental element in the construction of floating dwellings by the communities. Specifically, it is used as structural frames, flooring, weight distribution, and wall coverings, particularly on the Phumdi stage building type (see Figure 6). This preference for the material stems from its practical applications and functional qualities. Bamboo has a commendable level of sustainability, as it encompasses fourteen out of the fifteen accessible qualities, see

Table 4. Green features of bamboo.

Pre-Building Phase	Building Phase	Post-Building Phase
WR	CWR	B
P2	EE	R
--	WTC	RU
EER	NT	O
NM	RES
	LL

.

In the ‘Pre-Building Phase’, the bamboo has four out of five green features available. (WR+): Processing harvested raw bamboo into building materials is a simple and short process so as not to generate large waste. (PP+): Local bamboo cultivators cut and process bamboo manually or mechanically without emitting a significant number of pollutants into the air, water, or soil. (RC−): Bamboo is a renewable material, but it does not contain recycled content in the process of manufacturing the raw bamboo. (EER+): Low embodied energy is present in bamboo because it requires little refining and transport energy. (NM+): Bamboo possesses the characteristics that allow it to be classified as a natural material.

During the ‘Building Phase’ bamboo has six out of the six existing green features. (CWR+): Bamboo waste generated from construction activities has the potential to be repurposed for a diverse range of applications, such as fodder and fuel. (EE+): The method of assembling bamboo during construction necessitates minimal energy expenditure, mostly relying on physical labour. (WTC+): The utilisation of bamboo in construction processes does not entail the use of water, hence mitigating any potential impact on the surrounding water quality. (NT+): Bamboo is classified as a non-toxic building material. (RES+): Bamboo is a substance with low heat conductivity, and its high fiber structures make it a material that satisfies the passive-cooling mechanism. (LL+): Bamboo has a significantly extended lifespan and heightened durability when subjected to appropriate treatment. Specific types of bamboo species, such as “Saneibi” (bambusa nutans), “Khok” (bambusa mizorameana), have a very long life.

In the ‘Post-Building Phase’, bamboo shows four of the four existing ‘green features’. (B+): Because of the organic matter it contains, bamboo is relatively easy to decompose in nature in the soil, although it takes a while. (R+): Bamboo possesses sufficient durability to undergo recycling for the purpose of creating alternative goods after its first use, while also exhibiting inherent natural properties that enable complete biodegradation inside landfill environments [28]. (RU+): Due to the high durability of used bamboo, it can still be re-utilised for new building construction and other products. (O+): There are around 44 kinds of bamboo species found growing in both the valley and hills of Manipur. Bamboo is classified as a local and renewable material [29].

3.4. Plastic Barrels

The footing of the floating house design is a substructure that supports the building’s entire weight and allows the house to levitate. There is a range of materials that can be utilised as the foundation of a floating house, among which plastic barrels are included [30]. In Loktak Lake, there are contemporary methods for building a floating house on a plastic barrel flotation platform, see Figure 7. Plastic barrels provide favourable buoyancy characteristics, have a lightweight nature, and are readily accessible due to their widespread availability in our surroundings. However, plastic barrel has a sustainability level that is quite low because it has seven out of the total fifteen ‘green features’ that exist, see

Table 5. Green features of plastic barrel.

Pre-Building Phase	Building Phase	Post-Building Phase
--	CWR	--
--	EE	R
RC	WTC	--
--	NT	--
--	--
	LL

.

In the ‘Pre-Building Phase’, a plastic barrel has only one of five green features available. (WR−): The fabrication of plastic barrels, which primarily utilise high-density polyethylene (HDPE), is a lengthy process that involves raw material extraction, burning, shipping, and more. HDPE facilities generate solid industrial waste from manufacture, maintenance, and other operations. This trash hinders petrochemical sector growth [31]. During the manufacturing process, injection moulding, blow moulding, and assembly are involved. These processes produce trash, damaged goods, and non-reusable plastic. Trimming and finishing may also produce plastic leftovers. Indeed, contamination and mixed components prevent direct recycling of plastic garbage [32]. (PP−): The process of making plastic barrels plaster also produces pollutants. Inadequate waste management practices during production can result in several types of pollution, including the contamination of groundwater, deterioration of air quality, and the release of greenhouse gases like methane gas [33]. (RC+): Plastic barrels may be manufactured using a diverse range of plastic resins, such as HDPE and Low-Density Polyethylene (LDPE), among other options. Manufacturers have the potential to integrate recycled plastic materials, such as post-consumer recycled (PCR) plastic or post-industrial recycled (PIR) plastic, into their manufacturing operations as a means to mitigate the need for virgin plastic and divert plastic waste away from landfills [34]. Thus, it does have recycled content. (EER−): Plastic barrels have a very high embodied energy. The production process of plastic barrels requires energy, predominantly in the form of electricity and, in certain instances, heat. The energy consumption involved in the manufacturing of plastic barrels is associated with multiple stages within the production process. These stages encompass the polymerization of plastic materials, the transformation of plastic into barrels through techniques such as injection moulding or blow moulding, the subsequent cooling, trimming, finishing, and the implementation of quality control measures [35]. This observation is appropriate for evaluating both energy usage and its corresponding environmental effects. (NM−): Plastic barrels are classified as a non-natural material because their raw material, polyethylene (PE), is a synthetic material that is typically derived from petrochemicals, such as crude oil or natural gas, through various chemical processes [36].

In the ‘Building Phase’ Plastic barrels have five of the six existing features. (CWR+): During the construction of the floating building’s foundation, the plastic barrels must be evenly spaced to ensure stability. A fixed number of barrels will be required based on the size and buoyancy of the floatation platform, like the Nigerian floating school [37]. No extra waste will be generated during the attaching process. (EE+): The assembly of plastic barrels during the construction process of a floating foundation does not require too much energy because it is mostly done manually. (WTC+): Manufacturing plastic barrels requires water, but during the building phase, the assembly of the barrels is carried out with a dry system involving no water at all, so it does not impact the water quality around the site. (NT+): No phthalates or bisphenol A(BPA) are present in HDPE. HDPE is regarded as a safe and non-toxic plastic. It is widely used in numerous applications, such as food packaging, water containers, detergent bottles, toys, and milk containers, among others [38]. (RES−): Although floating plastic barrels may have creative potential for various applications, they are not widely acknowledged as primary building materials for natural energy-based building systems. (LL+): Plastic barrels are frequently developed with the intention of possessing robustness and being long-lasting. This practice effectively mitigates the necessity for frequent replacements and significantly decreases waste accumulation over an extended period; the estimated lifespan of the floating structure is 15 years [30]. However, the lifespan of HDPE plastic barrels used as floating materials in lakes can vary depending on the specific considerations related to their use in aquatic environments, water quality, maintenance and cleaning, and UV exposure. HDPE is frequently chosen for this purpose due to its buoyancy, water resistance, and durability.

In ‘Post-Building Phase’, the plastic barrels show only one out of the four existing ‘green features’. (RU−): Used plastic barrels cannot be reused in new construction. (R+): Used plastic barrels can be recycled; the recycling procedures include collection, cleansing, shredding, melting, and extrusion of waste materials. A diverse range of products may be manufactured using recycled plastic, such as fresh barrels, containers, pipes, and other items. Furthermore, it also reduces the demand for virgin plastic, which necessitates the extraction of fossil fuels [39]. (B−): Plastic does not readily decompose naturally when disposed of in the soil. Plastic barrels are not biodegradable. (O−): Plastic barrels are categorized as non-local material and contain non-renewable base material.

3.5. Corrugated Metal Sheet

In today’s society, galvanised steel structures are commonly used for exterior constructions such as collision barriers, light poles, fences, buildings, facades, and roofs [40]. Corrugated metal sheets and metal rods are commonly used as roof coverings for almost any type of waterfront building because of their lightweight and low cost. Corrugated zinc metal sheets have been serving several purposes in the construction of dwellings situated on the floating Phumdi of Loktak Lake in Manipur. They are often used in construction for roofing, wall cladding, structural reinforcement, and other purposes, see Figure 8. Overall, materials have very low sustainability levels because they only have eight out of the total fifteen features available, see

Table 6. Green features of corrugated metal sheet.

Pre-Building Phase	Building Phase	Post-Building Phase
--	CWR	--
--	EE	R
RC	WTC	RU
--	NT	--
--	--
	LL

.

In the ‘Pre-Building Phase’, only one of five green features is available. (WR−): The steel industry necessitates a multifaceted and protracted procedure, resulting in the generation of substantial waste as a consequence of its manufacturing processes. Thus, the coke oven by-product plant, sinter plant, refractory materials plant, blast furnace (BF), basic oxygen furnace, steel melting shop (SMS), and rolling mill are the main sources of solid waste generated by the steel industry. Steel industry solid wastes are categorised as coke and coal dust, BF slag, SMS slag, mill scale, refuse, oil sludge, fly ash, acid sludge, and refractory wastes, among others [41]. (PP−): Throughout the manufacturing process, the steel industry produces enough pollutants into the air, water, and soil. The act of depositing solid waste in open areas and excavated land results in the generation of environmental pollution in the form of dust particles and leachate. Additionally, this practice incurs significant financial obligations [42]. As one of the main industrial sources of CO₂ emissions, the iron and steel industry accounts for approximately 25% of industrial sectors’ direct greenhouse gas (GHG) emissions worldwide [43]. (RC+): Some types of steel materials have recycled content. The use of recycled iron and steel scrap is an essential primary resource for the manufacturing of new steel products, needing significantly lower energy consumption compared to the manufacture of iron or steel products derived from iron ore [44]. (EER−): The energy demands in a corrugated metal sheet factory generally encompass many processes, such as the Galvanisation process, Rolling and Forming, Cutting and Shearing, Stamping and Embossing, Coating and Painting, Cooling and Ventilation, Material Handling and Transportation, Lighting and Facilities, and Maintenance and Support Systems. Considering a complex and very long production process, corrugated zinc metal sheets contain a lot of energy, including energy for transport to the building site [40]. (NM−): Because the manufacturing process is time-consuming and labour-intensive, corrugated zinc metal sheets are considered to be inorganic materials.

In the ‘Building Phase’, corrugated zinc metal sheet shows five of the six existing green features. (CWR+): Corrugated sheets are manufactured to exact specifications pertaining to dimensions such as thickness, length, width, and zinc coating, in accordance with the given requirement. These products are provided in standard-modular dimensions in order to reduce the amount of waste produced during the process of field assembly. (EE+): During the building phase, the assembly of the structure does not require a significant amount of energy as it is predominantly carried out by physical labour. From an environmental perspective, this provides several notable benefits. These include a minimal environmental footprint during manufacture, the capacity to be renewed, natural decomposition, and a significant reduction in energy use during processing and transportation. The installation of metal sheets does not require a substantial energy input, as it mostly relies on manual effort [45]. (WTC+): There will be no impact on the local water supply because the construction process is carried out using a dry approach that does not include the use of water. (NT+): Metal sheets with corrugations are commonly galvanised or coated with zinc to prevent corrosion [46]. Zinc had been applied to metallic surfaces through either a hot-dipping or an electroplating process [47]. Galvanised coatings may have zinc compounds, although zinc is not considered highly toxic. As a result, corrugated zinc metal sheets are classified as construction materials that possess non-toxic properties. (RES−): The heat flow that occurs on corrugated zinc metal roofs is significantly high, with the temperature range spanning 24.9 °C to 57 °C. Due to its high heat conductivity, the use of steel as a base material is incompatible with the implementation of a passive-cooling strategy [48]. (LL+): The corrugated zinc metal sheet is a material that has a long lifespan, as shown by the manufacturer’s claim of around 30 years. Galvanised sheets have a much longer service life in comparison to bare, uncoated steel sheets. The results of a weather resistance test indicate that galvanised steel sheets show a much slower rate of deterioration compared to uncoated steel sheets, with a range of 5 to 30 times slower [49]. This increased durability and susceptibility to rusting contribute to its relatively longer lifespan.

In the ‘Post-Building Phase’, corrugated zinc metal sheet shows two ‘green features’. (B−): These roofing materials are primarily composed of non-biodegradable metals, such as steel and aluminium. In addition to protecting the metal from corrosion, the zinc coating is applied, and zinc itself is not biodegradable. (RU+): The practice of reusing corrugated galvanised iron sheets was commonly observed, particularly in cases where the sheets were obtained from structures that had undergone significant deterioration [50]. Nevertheless, the potential for corrugated zinc metal sheets to be reused is dependent on a range of factors. This pertains to factors such as the condition of the sheets, procedures for their removal, and techniques for cleaning and maintenance. (R+): Corrugated metal roofs with zinc coating possess recyclability characteristics, rendering recycling a viable and environmentally conscious approach for managing these materials upon reaching the end of their life cycle [51]. The scraps of galvanised steel, tin, and cast iron are treated separately from other scrap flows and are assumed to be fully recyclable for their original end uses [52]. (O−): It can be categorized as non-local materials and contains non-renewable base materials.

Figure 9 shows the comparison of green features among the five main materials of the Loktak Lake waterfront building. It is clear from this that there are three high-sustainability materials, i.e., Phumdi has the highest sustainability with 15 green features, followed by wood and bamboo with 14 features. These three materials are natural materials because their main contents are natural materials. Meanwhile, there are two materials with low sustainability performance: plastic barrels with seven features and corrugated zinc metal sheets with eight features. These two materials are non-natural materials with the main content of artificial materials. The greater the natural content of a material, the more green features it has.

4. Conclusions

This research examines the green features of Phumdi, highlighting its potential as an environmentally friendly and distinctive design element as well as a sustainable building material. In general, the rising need for sustainable building materials from the building industry leads to active research and development activities that make it possible to use a broader range of materials to meet the high demand for design requirements, such as fast-growing bamboo.

There are several kinds of floating dwellings in different parts of the world, each characterised by a unique construction technology and material usage. For instance, the Uros people use totora culms for building dwellings, boats, and islands, while the Tanka ethnic group in Aberdeen uses timber, bamboo, and wooden slabs for boathouses. Cambodia’s floating villages use bamboo frames, palm leaf panels, and metal barrels, and Vietnamese stilt houses use bamboo, wood, plywood, oil drums, and corrugated metal sheets. From a technological perspective of material utilisation, the majority of floating building designs use natural elements and are created using traditional techniques in a similar manner as that of the Phumdi hut construction style observed in Loktak Lake, India.

In all the stages of ‘material’s life cycle’, ‘pre-building phase’, ‘building phase’, and ‘post-building phase’—green features determine a material’s sustainability value. Materials incorporating natural ingredients, such as phumdi, wood, and bamboo, possess more green features and greater sustainability value. On the other hand, non-natural materials like plastic barrels and corrugated zinc metal sheets have fewer green qualities and poorer sustainability benefits.

In this line, one can imagine the floating phumdi as a naturally available resource that has the potential to meet a portion of the current building industry’s requirements, which eventually could lead to a reduction in the pressure on non-biodegradable materials. This study shows that using greener or more sustainable materials in a building increases its sustainability. The floating Phumdi houses have the highest sustainability value of the two waterfront buildings in Loktak Lake—wooden stilt houses and floating barrel houses—because most of their construction is made of Phumdi and bamboo.

Phumdi is a renewable, long-term material source with low environmental effects if managed appropriately. The study presented here aimed to organise and disseminate the information in order to encourage future research and highlight possible benefits and limitations that must be solved for the subject to be helpful in modern floating design.