A Review of Recent Advances in the Application of Cereal Straw for Decarbonization of Construction Materials and Applications

Abstract

The construction sector accounts for 39% of GHG emissions, being the main contributor to embodied carbon emissions of building materials, and operational energy consumption for indoor thermal comfort. Cereal straw, an agricultural by-product, is emerging as a low-carbon alternative due to its thermal performance and negative embodied carbon. This paper aims to review recent advances of cereal straw as a building material for decarbonization of construction, analyzing its thermal properties, embodied carbon, and large-scale applications. A literature review focused on European-certified straw-based materials, grouped into four categories: straw bales, blown-in insulation, modular systems, and bio-composites. Twelve Product Environmental Declarations (EPDs) and technical specifications were examined to evaluate manufacturing processes, material properties, and Global Warming Potential (GWP) for cradle-to-gate stages (A1–A3), as well as their use in large-scale projects over the past five years. Thermal conductivity ranged from 0.043 to 0.068 W/m·K, while embodied carbon varied between –101.2 and –146.5 kg CO₂ eq/m³. Straw bales remain prevalent in small-scale housing, blown-in insulation supports retrofitting, and modular systems offer the most balanced performance, enabling high-rise or extensive built surfaces. The study concludes that straw products have the potential to decarbonize opaque elements of the envelope, reducing operational and embodied energy of buildings.

1. Introduction

The building sector is responsible for a large scale of global CO₂ emissions, with an estimate of 39% of total emissions by 2020, of which 28% is for building operations and 11% for building and construction materials [1]. To reduce greenhouse gas (GHG) emissions of buildings, it is essential to address not only the operational energy consumption but also their full life cycle, including the embodied GHG emissions from the manufacturing and processing of building materials [2]. Over the last ten years, efforts have primarily targeted lowering the carbon emissions produced during building operation, while the embodied carbon in new constructions has become a major source of total emissions, accounting for 50% of the whole life cycle emissions [3]. A study of global trends analyzed the Life Cycle Assessment (LCA) of 238 buildings, built between 2005 and 2019, and shows that on absolute terms, embodied GHG emissions have risen from about 6.7 kg CO₂-eq/m²per year in existing buildings to between 6.7 and 11.2 kg CO₂-eq/m²per year in new residential buildings [2]. A Global Status Report for Buildings and Construction 2024/2025 [4] highlights the pressing need to align building codes, expand the use of low-carbon materials, promote fair access to green financing, and encourage circular construction practices. Decarbonization includes transitioning to sustainable, low-carbon, or carbon-negative building materials to help achieve global climate goals.

Insulation materials play a crucial role in reducing building energy consumption, but their production can have significant environmental impacts. Life Cycle Assessment (LCA) studies comparing various insulation materials have shown that mineral wool generally has the best environmental performance, while expanded polystyrene tends to have the highest impact [5]. However, bio-based insulation materials are emerging as promising alternatives with lower carbon emissions and good thermal performance [6]. Renewable insulation materials, such as those made from straw, seaweed, grass, reed, and recycled jute fibers, have shown fewer environmental impacts compared to conventional materials, particularly in terms of GHG emissions [7].

Straw-based materials, byproducts of cereal, represent a highly sustainable option for construction, offering numerous advantages as a bio-based alternative. Straw is carbon-negative, capturing and storing carbon dioxide during plant growth, which significantly reduces the overall carbon footprint of buildings [8,9,10]. Additionally, straw provides good insulation due to its low thermal conductivity [11,12], helping to minimize operational energy consumption and maintain indoor comfort [13,14,15]. Its production and processing require minimal energy, reducing reliance on synthetic materials and lowering environmental impacts [16]. As a byproduct of existing agricultural activities, straw does not demand additional land use, making it a resource-efficient choice that limits natural resource extraction [17]. Furthermore, straw-based construction supports a circular economy by reusing agricultural waste, reducing raw material extraction, and enabling recycling or natural decomposition at the end of its life cycle, thereby minimizing construction waste [18]. This review aims to support these arguments with a particular focus on decarbonization.

Although numerous studies have examined straw as an alternative to conventional construction materials, there remains a significant gap in comprehensive reviews of straw-based products that assess their environmental performance using standardized metrics such as Environmental Product Declarations (EPDs). Additionally, existing research often focuses on small-scale applications, leaving limited evidence on their feasibility for large-scale projects. This review addresses these gaps by analyzing European-certified straw-based products across four categories—straw bales, blown-in insulation, modular systems, and bio-composites—using verified EPDs and technical documentation. The study evaluates thermal conductivity and cradle-to-gate Global Warming Potential (GWP Total) and examines their implementation in large-scale projects built in the last five years. This approach provides performance benchmarks and identifies pathways for scaling straw-based solutions in contemporary construction.

The objective of this paper is to assess the potential of cereal straw as a building material for decarbonizing the construction sector, focusing on its capacity to reduce embodied and operational carbon in buildings through certified products and real-world applications in the European context. The review was conducted in three stages (Figure 1).

Firstly, a literature review of approximately 80 highly cited papers published between 2020 and 2025 was conducted using keywords such as embodied carbon emissions, life cycle assessment, straw construction, thermal performance, and sustainable building materials. Secondly, we performed mapping and evaluation of 16 commercial straw-based products available in Europe, classified into four groups (straw bales, blown-in insulation, modular systems, and bio-composites). Thermal properties and GWP Total (A1–A3) data were obtained from verified EPDs and the Eco Platform database, following EN 15804 standards [19]. Thirdly, we conducted an application review through the identification of large-scale projects (≥225 m², public use or infrastructure) built between 2020 and 2025, assessing the advantages and limitations of straw-based solutions in practice.

2. Literature Review of Straw as a Sustainable Construction Material

2.1. Agrowaste and Cereal Fiber Availability

Straw, the leftover stalk after grain harvest, is a versatile bioproduct sourced from various cereal plants [8], being recommended for straw-bale construction, and can be derived from wheat, barley, rye, rice, oats [20], triticale, and rice. It lacks nutritional value and is primarily utilized as bedding for livestock, as a crop for biomass energy [21], or incorporated into soil to enhance organic carbon content [22]. Straw is a sustainable building material because it stores carbon dioxide, requires little energy to harvest and process, and can be reused, repurposed, or naturally decomposes at the end of its life. However, rice cultivation and fertilizer use are important sources of GHG emissions, particularly rice is responsible of 10% of methane and 7% from decomposition in landfills [23], while fertilizers and burnt biomass produce nitrous oxide [24].

Straw is abundant throughout Europe, with approximately 270.9 million tonnes of cereals harvested in the EU in 2022 [25]. In 2022, France was the top EU cereal producer with 59.9 million tonnes (22%), followed by Germany (43.5 million tonnes, 16%), Poland (35 million tonnes, 13%), and Spain and Romania, each with about 7% [25]. Figure 2 presents the production of main cereals in the EU between 2012 and 2022, identifying million tonnes per type of cereal.

The EU harvested 126.7 million tonnes of common wheat and spelt in 2022, while the production of barley was 52.0 million tonnes [25]. In a smaller amount, the production of oats and rye was 7.5 and 7.8 million tonnes, respectively.

The choice of straw species used in construction materials is determined by the local abundance of straw suitable for large-scale building projects [26]. In Europe, the most common cereals used for construction are wheat, barley, and triticale [27,28,29,30]; in Asia, wheat and rice [26,31,32]; in the USA, rice, wheat, and oats; in South America, wheat and barley [33,34]; in Oceania [35] and Africa, wheat, barley, and rice [36,37].

In Europe, wheat is often preferred for its high availability, favorable hydrothermal behavior, long stems, and medium resistance. Extensive production is accompanied by numerous straw processing facilities, such as those producing chips for animal care, and its widespread use in construction. For instance, the EU Up Straw project has identified roughly 287 suppliers of construction-grade straw bales across Western Europe [38], highlighting the material’s significant presence in the building sector [39]. The French Straw Building Network (RFCP) specifies that only 1% of the straw produced in France is used to insulate 10% of new buildings [40].

2.2. Chemical and Physical Characterization

Chemically, straw is composed mostly of cellulose and lignin, the same major components of wood [8,30]. The chemical composition (

Table 1. Composition of different types of straw (%). Source: [13,41].

Straw Type	Cellulose	Hemicellulose	Lignin	Water Soluble	Ash	Wax
Wheat	38.6	32.6	14.1	4.7	5.9	1.7
Rice	36.5	27.7	12.3	6.1	13.3	3.8
Barley	34.8	27.9	14.6	6.8	5.7	1.9
Oat	38.5	31.7	16.8	4.6	6.1	2.2
Rye	37.9	32.8	17.6	4.1	3.0	2.0

) of straw fibers primarily includes cellulose (34–39%), which provides thermal insulation; hemicellulose (27–33%); lignin (12–21%), responsible for mechanical stability; moisture (4–7%); and ash (3–13%) [41,42]. It is covered by a layer of very thin and slightly water-repellent wax [43].

With regard to the morphological and functional properties, straw fiber is a porous, multi-layered material commonly recognized for its hygroscopic properties [44]. This porous structure allows it to interact with the surrounding humid air, facilitating the exchange of water vapor and helping to stabilize fluctuations in relative humidity, thereby enhancing indoor comfort [13]. A scanning electron microscopy comparison of wheat and rice straw cross-sections reveals distinct structural differences. Wheat straw exhibits larger cells with more size variation and a smoother surface texture compared to rice straw [13,32].

2.3. Embodied Carbon of Material

Straw-bale buildings can reduce embodied carbon by up to 76% compared to conventional buildings, and their embodied energy is about half that of traditional wall systems [13,14,15,16]. Straw materials are being integrated into nearly zero-energy buildings, demonstrating their potential to significantly reduce energy consumption and carbon emissions [45,46]. Each kg of straw is able to sequester 1.35 kg of CO₂ [29].

GWP-total measures the product’s total combined warming impact of all greenhouse gases (GHGs), expressed as carbon dioxide equivalents. Stages A1 to A3 account for all greenhouse gas emissions from raw material extraction, transportation, and manufacturing.

The Center for Industrialized Architecture (CINARK) at the Royal Danish Academy has developed a digital version of the Construction Material Pyramid to visualize the environmental impact associated with the production of materials [47], based on EPDs of Northern Europe.

Table 2. Comparison of the environmental impact of insulation construction materials, GWP corresponding to life cycle phases A1 raw material supply, A2 transport, and A3 manufacturing. Source: ref. [47].

No.	Material	Group	GWP-Total A1–A3 (kg CO2-eq/m3)
1	Straw	bio-based	−127.0	Climate-negative
2	Paper wool	bio-based	−72.0
3	Wood fiber insulation	bio-based	−61.1
4	Eelgras/zostera	bio-based	−49.9
5	Glass wool	mineral	12.8	Climate-negative
6	Hemp fleece/PE	bio-based	14.2
7	Expanded perlite	mineral	20.9
8	EPS insulation Graphite 80	plastic	46.8
9	Wood cement	bio-based	51.6
10	Stone wool	mineral	68.7
11	Phenolic foam	plastic	74.7
12	PUR/PIR	plastic	93.3
13	XPS insulation	plastic	94.0
14	Foam glass	mineral	239.2

shows climate-negative and climate-positive insulation materials, with their total Global Warming Potential (GWP-total) corresponding to life cycle phases A1 raw material supply, A2 transport, and A3 manufacturing.

Life cycle assessments (LCA) consistently show that straw-based construction materials have a much lower carbon footprint than petrochemical-based or standard building materials [13,14,15,16]. Bio-based insulation materials like straw (−127.0 kg CO₂-eq/m³), paper wool, wood fiber, eelgrass, can sequester more carbon [47] than is embodied in construction, therefore having a negative carbon footprint. Research shows that straw-based building elements have high biogenic carbon content and fast regrowth cycles, making them particularly promising for carbon fixation and reducing embodied GHG emissions compared to conventional materials like brick or concrete [48].

Straw bale construction in residential housing exhibits lower life cycle carbon impacts than conventional materials. The study by Kozień-Woźniak et al. [49] quantified a reduction of 94.73 kg CO₂ in the production of straw bales for a single-family residential building in Poland. Findings by Cornaro et al. [16] revealed production (A1–A3) and construction of a straw-bale wall accounted for 50% lesser embodied energy and CO₂ emissions than a masonry wall. Additionally, Vanova et al. [17] on the LCA of phases A1–A3 of a residential building in Italy, calculated a saving of 80% lower CO₂ versus a masonry wall.

2.4. Energy Efficiency and Thermal Performance

Straw-bale and straw-composite walls provide excellent thermal insulation, leading to energy consumption reductions of up to 83% in some climates [13,14,15]. Operational assessments revealed a 61% drop in CO₂ emissions over 60 years [10], and annual savings of 1230 kg CO₂ [9]. Additionally, data on carbon storage notes that a house built with straw bales may sequester over 15 tonnes of CO₂ [10].

Straw bales offer good thermal insulation, making them a viable alternative to conventional building materials [8,9,45]. A study of biobased insulation materials showed wheat and rice straw among the more sustainable, with a thermal conductivity of 0.034 W/Km and 0.043 W/Km, respectively [50].

Table 3. Thermal performance, embodied energy, and GWP of fired bricks, concrete blocks, and straw bales for 1 m² of wall. Source: ref. [51].

Number Required per m2 of Wall	Thermal Conductivity (W/m·K)	Thermal Transmittance (W/m2·K)	Embodied Energy (MJ/m2)	Global Warming Potential (kgCO2-eq/m2)
85 Fired bricks	0.9	3.9	488 1	30
11 concrete blocks	0.64	3.2	169 2	9.6
3 straw bales	0.07	0.16	28	2.5

¹ Include 700 km transport. ² Include 700 km transport in 10% of the weight due to cement.

compares straw-bale construction with conventional construction systems using more traditional materials, exemplified in an ideal wall element, per square meter.

The comparison of straw bales, fired bricks, and concrete blocks in Andean Patagonia found that the straw-based materials had lower carbon emissions and embodied energy per square meter of wall, and superior thermal performance [51].

In the review conducted by Sun et al. [26], 13 straw-bale structures were systematically analyzed using on-site thermal measurements across countries with Oceanic, Mediterranean, humid-continental, and humid-subtropical climates. Of these, nine buildings operated without indoor heating or cooling systems. In the Mediterranean, Oceanic [52], and humid-subtropical regions, straw-bale constructions demonstrated effective thermal performance, maintaining indoor temperatures between 15 °C and 28 °C despite outdoor fluctuations. Conversely, in humid-continental climates, straw-bale buildings face significant challenges during both winter and summer due to extreme temperatures [53], requiring additional operational energy to ensure thermal comfort.

In terms of thermal performance, the following parameters had been reviewed by Tlaiji [9]: straw-bale thermal conductivity (λ), heat capacity (Cp), and thermal diffusivity (α) versus density (ρ), moisture content (MC) or relative humidity (RH), temperature (T), and the fiber type and orientation. Fiber types included wheat, rice, and barley, and fibers oriented perpendicular, parallel, or random to the heat flow direction. The results documented thermal conductivity values for straw bales ranging from 0.03 to 0.19 W/(m⋅K), while densities were 100–150 kg/m³, with an ambient temperature and RH range of −5 to 40 °C and 5–60%, respectively [9,31,54].

Research conducted by Sabapathy and Gedupudi [31] is the only study that simultaneously examined the impact of multiple variables on the thermal conductivity and thermal diffusivity of straw bales. Their investigation considered factors such as bale density, orientation, ambient temperature, and relative humidity. Samples were prepared with densities ranging from 50 to 95 kg/m³ and were oriented in three ways: perpendicular, random, and parallel. The thermal conductivity and thermal diffusivity of these samples were measured using the transient plane method at temperatures from 25 °C to 45 °C and relative humidity levels from 0% to 80%. Among all the variables analyzed, bale orientation was found to have the most significant effect on both thermal conductivity and thermal diffusivity. Interestingly, the samples oriented randomly and perpendicularly displayed similar thermal insulation properties and trends, while the parallel-oriented samples showed distinct differences. Specifically, under high humidity conditions of 80% RH, the thermal conductivity values for the random and perpendicular orientations increased by 1.5 times, while for the parallel orientation, the increase was 2.5 times compared to the dry state [13,31]. Moreover, a polynomial function (1) was determined for the parallel-oriented straw [31].

λparallel = 0.0103ρ2 + 2.196ρ + 1.573(%RH) + 0.478 T 46.072 [mW/(m⋅K)]

(1)

In conclusion of this subsection, as straw bales are not an industrial material, it is difficult to standardize their thermal performance. Variability of results may arise from factors such as the types of straw used, density of the bales, orientation in relation to heat flow, as well as the ambient temperature and relative humidity [13]. It is recommended to work with ranges determined by straw-bale construction standards, described in Section 3.1.

2.5. Natural Resources Extraction and Circular Economy

About 30% of global extraction of natural resources is used in construction, primarily for buildings and infrastructure materials, while 25% of solid waste is generated [55]. Straw-bale construction significantly reduces the extraction of natural resources because it reuses an agricultural byproduct that would otherwise be considered waste, thereby lowering the demand for conventional, resource-intensive building materials like concrete and steel [17,18]. This approach supports the principles of a circular economy by reducing construction waste, enabling the reuse of agricultural residues, and allowing for recycling or energy recovery at the end of a building’s life [18]. Regarding the “reduce” principle, straw-bale buildings help minimize construction waste, lower environmental impacts, and decrease energy use and carbon emissions. In relation to the “recycle” principle, straw-bale structures can be used as compost or processed through physical, biological, or thermochemical conversion methods, producing materials such as wood composite boards as well as biogas and biomass fuels for power generation and heating [18].

The environmental impact of straw-bale construction is generally low, especially when straw is sourced locally, minimizing transportation and associated emissions; however, the ecological footprint can vary depending on the origin of the straw, with straw from extensively cultivated pastures having a higher ecosystem impact than that from intensive crop production [17]. In terms of land use, straw-bale construction does not require additional land for raw material production, as straw is a byproduct of existing agricultural activities, making it a land-efficient building material [17,18]. Regarding water consumption, the literature does not provide direct quantitative comparisons.

2.6. Enhancing Durability and Fire Safety

Durability and fire risks are general concerns for large-scale adoption of straw construction. Straw-bale construction began in the late 19th century in the United States for homes, churches, and schools [43], many of which remain in good condition [43]. There are two stages to ensure durability: one is the quality of the material, and the second is the application in construction.

Firstly, after harvest, it is important to separate cereal from fiber for storage, to avoid mite or xylophagous attack [56]. Fiber storage protected from water is also important. There is no need for chemical and physical pretreatments. Straw-bale quality, including density and humidity, will be reviewed in Section 3.1. Secondly, to ensure the durability of straw in buildings, it is recommended to apply interior and exterior coatings for protection against insects, moisture, and fire [43], as well as to maintain separation from the ground and prevent direct water exposure. Regarding durability improvements, Cascone et al. [30] reported that high-density lime or clay renders improve moisture resistance without compromising insulation.

Literature indicates that fire resistance has been improved through plastering techniques and densification processes [57]. Standardized testing protocols (EN, ASTM) have validated that properly rendered straw-bale walls can meet or exceed fire safety requirements for residential and commercial applications. Density of bales with their relation to fire resistance, structural integrity, and insulation will be discussed in Section 5.1.

2.7. Limitations of Current Studies

Current research on straw-based construction faces several key limitations affecting the understanding of thermal performance and decarbonization potential. One major issue is the variability in straw properties, such as fiber orientation, density, and moisture content, which significantly influence thermal conductivity and hygrothermal behavior but are inconsistently reported or controlled across studies [31,58,59]. Variability in straw properties hinders the development of reliable thermal conductivity models and standardized performance metrics. Many studies are geographically narrow, which limits the generalizability of results and optimization for diverse conditions [15]. Furthermore, research often concentrates on small-scale or laboratory settings rather than whole-building performance, restricting insights into real-world energy savings and decarbonization potential [29,46]. Addressing these gaps requires comprehensive, standardized, and climate-adapted studies to fully realize the sustainability benefits of straw-based materials.

3. Straw-Based Building Materials and Products

In this next stage, this paper mapped companies and manufactured products available mainly on the European market based on cereal straw. The products were classified in four groups, according to the technological and complexity level of manufacturing: straw bale, blow-in, modular systems, and biocomposite boards (Figure 3). Each group has a description of manufacturing processes, thermal conductivity, and Global Warming Potential (GWP) for cradle-to-gate stages (A1–A3).

Companies involved in the supply of straw-based materials and products for construction are widespread in Europe, offering a range of solutions with straw bales, modular systems, blow-in straw, and manufactured boards and batts [39]. Figure 4 shows 10 companies that manufacture modular systems and 11 biobased materials. The second one is mostly in central Europe.

3.1. Straw Bale

The production of straw bales encompasses all farming activities, from soil preparation, cereal sowing, crop cultivation, and grain harvesting [63]; finally, bales created from straw waste are left in the field after crop harvesting. Baling machines collect, compress, and bind these straw wastes into compact bales using steel or polypropylene twine [13]. This baling process allows to produce a wide range of density values, and it can also influence the orientation of the straw fibers within the bales.

Table 4. Straw bale characteristics according to regulations or technical guidelines.

Ref.	Regulation	Types of Straw	Dimensions 1	Density	Moisture Content
[20]	USA AS Strawbale Construction	Wheat, rice, rye, barley, oat	W: 460 mm H: 355 mm L: 914 mm	>104 kg/m3	<20%
[64]	Germany SBR-2024	Wheat, rye, spelt, triticale, barley	W: 480 mm H: 360 mm	85–115 kg/m3
[43]	France CP2012	wheat	W: 470 mm H:370 mm L: 500–1200 mm	>80 kg/m3	<20%
[22]	UK Straw Construction in the UK	wheat, barley, rye, oats, rice	W: 460 or 510 mm H: 357 or 380 mm L: 800–1200 m	>80 kg/m3	25%

¹ Dimensions of a straw bale laid flat.

shows recommended dimensions, density, and moisture content according to regulations or technical guidelines, to ensure durability, fire resistance, and thermal performance.

The USA, Germany, France, and the UK are some countries with specific regulations or guidelines for straw-bale construction, including AS Strawbale Construction [20], SBR-2024 [64], CP2012 [43], and Straw Construction in the UK [22], respectively. Other nations lack equivalent legal frameworks, creating inconsistencies and challenges in adopting this building method internationally.

According to regulations or technical guidelines, straw bales laid flat measure between 500 and 1200 mm in length, 460 to 510 mm in width, and 355 to 380 mm in height, depending on the baling machines. Recommended density is a minimum of 80 kg/m³ with a maximum humidity of 25%. The more compression, the more resistance to fire, but the less thermal performance. The trade-off between density and compression is critical: higher compression increases mechanical strength but may reduce insulation efficiency and alter fire response, while lower density favors insulation and fire resistance but may compromise structural integrity [65,66].

3.1.1. Construction Techniques

In construction, straw bales are utilized as insulation or structure mainly on the envelope of a building. The European Straw Building Association (ESBA) developed construction details (Figure 5) with straw bales used in different orientations, either as timber-frame infill or as load-bearing on their own. Techniques a and b are also replicated on prefabricated modules, using laminated or dual timber frames.

In the load-bearing wall (d), straw bales carry the weight of the roof, so this technique is mainly limited by the size of openings, which must not exceed 50% of the wall area, and by a typical height restriction to one story [9]. The nonstructural or infill methods: wood frame filling, cross-frame, or GREB technique, rely on a framework of wood or reinforced concrete columns and beams to bear the structural loads.

3.1.2. Properties of Straw Bales

Straw bales are difficult to standardize and certify as a product. Therefore, associations like German Straw Bale Construction Association (FASBA), Straw Building UK (SBUK), and French Straw Bale Construction Network (RFCP) published EPDs of straw bales, presenting thermal performance and embodied carbon (

Table 5. Thermal performance and embodied carbon of straw bales according to EPDs.

Ref.	Cereal Fiber	Dimensions (mm)	Thickness (mm)	Density (kg/m3)	RH	Thermal Conductivity (λ) (W/m·K)	Thermal Resistance (R) (m2K/W)	GWP-Total A1–A3
GE [63]	Wheat and Rye	H: 200–700 L: 500–3000	300–900	85–115	11.8%	0.043	-	−129.4 kg CO2-eq/m3
UK [68]	Wheat and Barley	H: 480 L: 800	370	100	-	0.052	7.1	−116.0 kg CO2-eq/m3
FR [69]	Wheat (organic)		370	80–120		0.052	7.1	−54.2 kg CO2-eq/m2

).

Thermal conductivity was declared between 0.043 and 0.052 W/m·K, and GWP total for cradle to gate stages −129.4 and −116.0 kg CO₂-eq/m³ in Germany and the UK, respectively. The lowest or negative GWP value is obtained in phase A1, for raw material supply. Biogenic GWP-b is −258 kg CO₂-eq/m³, carbon accumulated during the plant growth. In France, the declared unit was m^2, and the collective EPD embraces 99 manufacturers with organic agriculture.

3.2. Blow-In

Swiss, German, and Austrian companies provide blown-in insulation by processing straw. This system is cost-effective, low-to-medium-tech, thermally efficient, and has a low environmental impact. The process is similar to the cellulose application [70]; the fiber can be applied on-site or on prefabricated modular systems of different building components. It is suitable for new buildings and energetic rehabilitation, and can be used as cavity insulation for filling exterior walls, interior walls, ceilings, flat roofs, and sloping roofs [71].

3.2.1. Blow-In Manufacturing and Installation Process

Straw, an agricultural byproduct, undergoes technical processing to achieve a specific fiber shape suitable for blowing into hollow construction elements at a density of about 105 kg/m³, ensuring it does not settle over time. In blow-in straw, the stalks are split open to eliminate hollow sections, producing fibers roughly 30 mm long and 5 mm wide, with less than 10% fine particles under 1 mm. The material is also cleaned to remove dust and leftover grain [71]. The product is a dry, packaged insulation that meets standards and is protected during transport and installation (Figure 6(4)).

Regarding the construction and installation process, it involves filling cavities with chopped straw on timber frame construction (Figure 6(6)), ensuring high density during the application [72]. It is best installed in a covered workshop, but on-site installation is possible if weather conditions are managed [73].

3.2.2. Blow-In Properties

The development of blow-in insulation has primarily focused on its environmental impact and thermal properties (

Table 6. Characterization of straw blow-in according to specifications.

Ref.	Components	Cereal Fiber	Thickness of Wall	Density	Water Vapor Permeability	Thermal Conductivity (λ)	GWP Total A1–A3
[60,71]	Fiber max. 30 mm long	wheat	280 mm	105 kg/m3	μ = 2.8	0.0546 W/m·K	−146.5 kg CO2-eq/m3

). However, there is currently a lack of published research on the potential acoustic benefits of straw as a cavity-damping material in timber frame structures [72].

A study developed a thermal insulating material based on wheat straw (50%) and recycled paper cellulose (50%) with a thermal conductivity average of 0.036 W/m·K, at a density of 80 kg/m³ [74]. High density of fiber application over 100 (kg/m³) allows the material to be non-combustible, but increasing density decreases insulation properties [57].

3.3. Modular Systems

Ten companies manufacture modular systems with straw bales in Europe. They consist of prefabricated timber-framed structures (studs or CLT) filled with pressed straw, offering structural and insulating solutions. Prefabricating straw-bale infill walls allows materials and components to be processed in a standardized way, resulting in durable, high-performance wall systems while greatly improving production quality and efficiency [26]. Among modular construction systems, straw is the primary material used, applied in both low-tech and medium-tech solutions. Five manufacturers focused on straightforward applications of straw bales within timber frames, while the more widespread approach involved manually or mechanically filling modules with loose straw and then trimming the surplus [39].

3.3.1. Manufacturing and Installation Process

The manufacturing process for modular systems or prefabricated modules using straw typically involves compressing straw into dense bales or panels, which are then integrated with structural frames, often made of wood or other low-impact materials. For example, straw bales are compressed to densities above 90 kg/m³, providing both structural integrity and excellent insulation properties; these bales can be used as infill within wooden frames to create wall modules or panels for housing construction.

For the type of box walls, the construction elements consist of a combination of natural and engineered materials, including straw, timber, sheathing board, breather board, I-joists, and breather paper [75]. The core structure is formed by a timber frame, which serves as a skeleton for the panel. This frame is then filled with straw, which is carefully poured into the cavities to create a solid wall. The straw is subsequently compressed to ensure stability and prevent future settling.

Medium-sized modules commonly have a dual timber frame and straw infill. After the assembly on-site, the internal and external surfaces can be customized according to the client’s preferences, with the actual application of these finishes typically carried out by separate contractors. Several prefabricated straw-bale wall systems, including Ecostrauv and EcoCocon, have achieved advanced technological maturity and have been successfully implemented in many building projects [26,76].

3.3.2. Modular Systems Properties

The following data on

Table 7. Characterization of straw modular systems according to commercial specifications.

Ref.	Cereal Fiber	Dimensions (mm)	Thickness (mm)	Density (kg/m3)	RH	Thermal Conductivity (λ) (W/m·K)	Thermal Transmittance (U Value) W/(m2·K)	Load Bearing (tn)	GWP-Total A1–A3 (kgCO2eq/m2)
EcoCocon [77]	wheat	H: 2600 mm L: 700 (varies)	300–400	-	-	0.0645	0.123	11	−101.2
Ecopaja [78]	wheat	H: 2450 L: 1230–5000	240–450	135–185	<15%	0.068	0.144	33	-
Lorenz [79]		H: 2460–2760 L: 2560	180–340	100	<18%	0.049	0.298–0.162	3.5	-
Modcell [75]	wheat	H: 2700 L: 3000 (varies)	262–427	-	-	-	0.19–0.13	-	-
Activ Home [80]		-	300	-	-	-	-		−79.1
Okambuva [81]	wheat	H: 500–2900 L: 500–1200	250–350	120	<15%	0.067	0.198–0.166	3.5	−47.0

, was extracted from EPDs, commercial data sheets, and certificates, as product declarations from laboratory essays.

Modular systems are manufactured on different scales: small modules, entire walls, or medium-sized panels and box-type, mainly applied on walls, but also on the roof, floor, or partitions. All manufacturers used wheat straw. Panels’ height ranges from 2450 to 2900 mm, and length varies from 500 to 5000 mm. Straw densities are over 100 kg/m^3, and load-bearing modules have a resistance of up to 33 tonnes.

Only two providers of modular systems had an EPD. Even though the product has an industrialized manufacturing process, it is still climate-negative with −101.2 kg CO₂-eq/m². Specifications declared wall thickness ranging from 180 to 450 mm and thermal conductivity from 0.049 to 0.068 W/m·K. The product applied to the envelope could be wall, insulation, and structure at the same time, while reducing the embodied carbon of the material.

3.4. Straw Biocomposites

Straw composites are gaining attention, in which straw fibers are typically combined with various alternative binders, which may include biocomponent fibers, inorganic substances, synthetic resins, and natural adhesives [13]. In Europe, there are 11 companies that manufacture biobased construction materials and products with straw [39]. They are concentrated in Eastern Europe, predominantly in Austria, Germany, Switzerland, France, Italy, Poland, and Czechia. They produce a variety of materials and products across different technological levels, which primarily consist of dry boards and batts for timber frame applications [39]. A study carried out by Zheng et al. [11] confirmed the viability of incorporating straw boards into building envelope systems as alternative sheathing panels, capable of meeting both structural support requirements and thermal insulation needs.

3.4.1. Straw Boards Manufacturing Process

According to Zhou et al. [13], the typical production process for straw composites involves the following steps: first, processing the straw using techniques like cutting, smashing, crushing, or milling to produce short straw fibers, thereby facilitating mixing more effectively than using the raw, longer fibers; second, mixing the straw fibers either pneumatically, mechanically, or manually with binders and other functional materials; third, forming the insulation panels or boards, followed by a compression stage, which may include pressing [82], thermal pressing, or high-frequency hot pressing [83] to achieve the desired shape, stability, and density; and fourth, drying or curing the panels or boards either at room temperature or in an oven to expedite the process.

Paper straw boards (PSBs) are an improved straw-bale that consists of three main elements: outer sheathing paper, inner straws, natural binder, and air gaps. The board is encased in high-density pulp sheathing paper, which serves multiple functions: it constrains the inner straws, improves overall board integrity, enhances surface durability and smoothness, and shields the interior from external factors [11]. These features make PSBs more suitable for engineering applications than conventional straw bales. The air spaces within and between straw stems play a crucial role in the board’s exceptional thermal insulation and sound absorption capabilities. A board specification includes a thickness of 58 mm, a width of 1200 mm, a length of 3000 mm, and a density of 400 kg/m³ [11].

Wheat straw strand board (WSSB) has a higher technological process, which involves crushing straw stalks to create short fibers, incorporating a binding substance, and finally, the material is compressed into boards [11]. Isocyanate resin serves as the preferred adhesive, noted for its powerful bonding capabilities and low emission of toxic fumes such as formaldehyde. Specifications include length of 2440 mm, width of 1220 mm, thickness range from 12 to 30 mm, and densities from 1200 to 620 kg/m². Higher densities may contribute to better mechanical properties [11].

Straw insulation boards are composed of straw from Poland and 5% PMDI resin from Hungary, and are transported by truck to the production plant located in Poland. The manufacturing includes fragmentation, defibration, pressing, loosening, drying, and assembling processes [84]. For installing the product, as masonry or wall and roof external insulation, straw insulation boards 140 kg/m³ can be installed with lime plaster and screws.

3.4.2. Straw Composites Properties

Table 8. Properties of some straw composites in the European market.

Ref.	Product	Cereal Fiber	Binder	Thickness (mm)	Density (kg/m3)	Thermal Conductivity (λ) (W/m·K)	GWP-Total A1–A3 (kg CO2-eq/m2)
[84]	insulation boards	Triticale, rye	PMDI resin	43	140	0.043	−3.86
[85]	LDF Board	Triticale, rye	PMDI resin	30	280	0.055	−150
[86]	SSH100 Insulation boards	Wheat	No added binder	75/100/120	85	0.041–0.046	-
[87]	straw panels	Wheat	No added binder	38/58	379	0.099	-
[87]	straw MDF	Rice	4% PMDI, formaldehyde-free	9/12/18/25/30/35	700	0.114	-
[88]	RH50 (semi-rigid insulation panel)	Rice	8% polyester thermofusible fibers	45/200	50	0.039/0.045	-

presents straw-based biocomposites, specifically boards and insulation products, with properties and GWP extracted from EPDs and the technical data of some commercial products available in Europe. Plasters, renders, and finishes were out of scope of this study.

Insulation boards can be applied to facades, roofs, slabs, or partitions.

Available literature primarily addresses the effect of raw straw variability on binder performance rather than on the properties of the final boards. Binding is achieved by the natural lignin in the straw itself, which means straw boards are free of synthetic, potentially harmful glues. Manufacturing conditions, such as pressing temperature and time, must be optimized for each straw type and density to meet performance standards, as shown in binder-less boards from steam-exploded wheat straw [89].

4. Application on Large-Scale Built Projects

In Europe, 1400 straw buildings were mapped, most of them single-family homes located in France and Austria, and the most used straw-bale technique is infill construction [90]. Most straw buildings are found in countries that have established regulations for their construction [46]. The United States leads with 784 straw buildings, while France comes second with 700 [16].

The Up Straw project, developed by ESBA [67], promoted and supported the use of straw in urban and public buildings by conducting research, education, knowledge sharing, market development, and communication. It also featured five public pilot constructions that demonstrate various straw construction techniques and models of public procurement. These include the Country Park Visitor Centre in Hastings, UK, built using load-bearing straw-bale technique; the Roomley Sports Hall in Tilburg, Netherlands, insulated with blown-in straw panels; the new office of the Cluster Eco Construction in Namur, Belgium, constructed with modular straw panels; a new building at Plankstetten Abbey in Germany, also built with modular straw panels; and the renovation and construction of the straw-bale education center at the Maison Feuillette site in Montargis, France [73].

Figure 7 showcases five large-scale projects built between 2020 and 2025 with different straw construction materials and products: straw bale, blown-in, and modular systems. The projects include public buildings, high-rise, renovation, energy rehabilitation, and building areas up to 155,000 m², which show possibilities and recent advances in the application of straw in construction.

Most straw-bale buildings are one or two levels, as the structural properties of straw bales and common building practices make these heights practical and safe for residential use [94]. The method’s simplicity, affordability, and suitability for owner-builders make it a popular choice for small-scale [95]. The Bale House Hastings is a 225 m² public building, with a hybrid load-bearing construction technique. The distance between the straw supply and the project was 100 km, and the cost was 4000 €/m² by 2020 [73].

The blow-in technique is an innovative and sustainable choice to renovate with straw as insulation in a built environment. The Roomley Sports Hall in the Netherlands used prefabricated timber sections with 32 cm blow-in straw for renovation and extension. The renovation and extension had a cost of 1100 €/m², while the volume of straw was 260 m³, supplied 250 km from the project [73]. The mid-life upgrade aimed for a net-zero energy building and included wrapping two halls to use less energy to heat or cool the space with an insulation value of at least Rc 7 [73]. Supply chain logistics for straw-based materials can affect embodied carbon and project feasibility, mainly due to transport distances. Optimizing the supply chain requires strategic site selection for collection and storage to minimize costs and emissions [96].

Regarding modular systems, ETC Hyllie is a 12-storey high-rise apartment building, with a main structure of CLT at its core, and the external walls are straw modular panels for insulation and structure [91]. Henning Larsen Architects is building the Bestseller Logistics Center West in the Netherlands; once constructed, it will be the largest building with timber and straw modules, with a total built surface of 155,000 m² [92], and 40,900 m² of prefabricated panels. In 2025, a public building with straw modular systems in Spain, Ecoespai de Mont-roig del Camp, was awarded as Bioconstructed Public Equipment [97]. Ecococon is the provider of modular panels for the last three projects, which built 63,852 m² of walls by 2025 [76]. This value points to a small scale of manufacturing in the sector [26] but is increasing and represents a total sequestered carbon of 7,199,060 kg.

Another innovative project is Risorsa Towers in Italy, which develops an energy and social requalification on an eight-story building through anchoring modules on the existing external walls. The modules were made with recyclable or reusable natural materials like wood for the structures, along with rice biocomposites products for insulation and finishes [93]. Applied biocomposites were rice-based, including RH50 semi-rigid rice-straw insulating panels detailed in Table 5, and insulating thermal plaster composed of rice husk and lime.

These projects meet structural, safety, fire, and seismic codes or standards. Particularly, the multi-story building Hyllie project was designed in accordance with the Swedish National Board of Housing, Building and Planning’s (BBR) regulations [91], and Eurocodes with national annexes. EcoCocon panels acted only as non-load-bearing infill, while the primary load-bearing structure was CLT [98], designed under EN 1990 [99] Basis of Structural Design and EN 1991 [100] Actions on Structures [101]. A local engineer calculated and verified the fastening of preassembled EcoCocon elements, mainly using Rothoblaas connections, and planned on-site safety measures for lifting operations at 38 m height. Fire safety followed BBR, with a certified fire engineering firm (competency level 3 or 4) responsible for all calculations, simulations, and compliance, referencing EN 1995-1-2 [102] for timber structures [103]. Seismic loads were not a governing factor in Sweden due to low seismicity; however, for projects in seismic regions, compliance with European and local regulations would be required in collaboration with a qualified wood engineer. This integrated approach ensured full adherence to structural, safety, and fire performance standards for multi-story timber construction.

5. Discussion

The main contribution of this work is to show the application of straw-based materials for the decarbonization of construction, analyzing their thermal properties, embodied carbon, and large-scale applications in the European context. Straw is being applied on high-rise, in public buildings, large surfaces, or for energy renovation. This study contributes to showcasing the recent advances of straw construction, thermal performance, environmental impact, and the possibilities of application of straw products available on the market. Most of the literature focuses on performance, life cycle assessment, thermal conductivity, fiber, and others [46], evaluating mainly small-scale residential projects. However, some architectural practices, associations, and commercial products are innovating to upscale straw construction, and there is a gap in the literature regarding this information.

Since straw is derived from agro-industrial waste of cereal crops and is not a standardized material, its thermal performance and environmental impact data vary depending on the type of cereal, origin, cultivation method, baler harvest, and application on site. Based on the results, straw bales’ characteristics might be used within the ranges recommended by the standards AS Strawbale Construction, SBR-2024, CP2012 [43], Straw Construction in the UK.

5.1. Thermal Conductivity and GWP Overview of Straw-Based Materials

Figure 8 shows an overview of thermal conductivity and GWP of the four groups of products.

Negative GWP indicates net biogenic carbon storage exceeding emissions in A1–A3 (as reported in EPDs), so points below the zero line represent net storage. Straw has excellent thermal performance and reduces carbon emissions, not only reducing operational energy use but also addressing sustainability by lowering the overall environmental impact of buildings [13,14,15,16]. According to the results of straw-bale EPDs, thermal conductivity was declared between 0.043 and 0.052 W/m·K and GWP total −129.4 and −116.0 kg CO2eq./m³ in Germany and the UK for life cycle stages from cradle to gate. The thermal conductivity of straw usually becomes higher as the material is packed more densely, but this increase does not always happen in a straight line [66,104]. Literature showed ranges of 0.03–0.19 W/m⋅K for thermal conductivity [9,31,54] and GWP of straw manufacturing (A1–A3 stages) −127.0 kg CO₂-eq/m³ [47].

Thermal performance in plant-based fibrous materials is influenced by density, moisture content, and cereal type [105]. Higher density generally increases thermal conductivity because solid lignocellulosic pathways replace air pockets, reducing insulation efficiency. Moisture further raises conductivity, as water conducts heat better than air. Cereal type matters due to fiber geometry and silica content: hollow stems in wheat, barley, and rye improve insulation compared to denser husks. For design, straw bales’ optimal density ranges 85 to 115 kg/m³ [64] ensure fire resistance and structural integrity, while balancing insulation needs [54]. Lower-density bales offer better R-values but require thicker walls or additional reinforcement, making them suitable for non-load-bearing infill applications. Proper detailing, such as vapor-open finishes, raised foundations, and wide roof overhangs, supports moisture management, durability, and thermal performance. Conventional insulation materials such as mineral wool or expanded polystyrene typically have thermal conductivities in the range of 0.03 to 0.04 W/m·K [106], placing straw insulation in a similar performance category but with added environmental advantages [12].

With regard to quantitative research, a lack of a recognized numerical model for straw-bale thermal performance holds back accurate evaluation of indoor comfort and energy use in buildings [26]. For WLCA, gaps remain in end-of-life phase assessment and standardization of carbon storage accounting methods. Research should adopt comprehensive system boundaries (A1–D) and employ standardized databases (preferably Ecoinvent with consistent versions).

5.2. Construction Possibilities, Advantages, and Disadvantages with Straw

Among the four groups of straw products, modular systems showed larger versatility, efficiency, and the possibility to upscale application in the construction industry in Europe. The prefabricated product arrives at the construction site on different scales as panels, walls, roofs, or entire rooms (Figure 9). They can be applied to new buildings as load-bearing walls due to the timber frame, envelope infill, or for energy rehabilitation, acting as structure, walls, and insulation at the same time. Modular systems have been applied to large public, commercial, or educational buildings, with up to 155,000 m², six levels as load-bearing walls, high-rise complemented with CLT structure, or twelve levels with anchored modules to existing walls. In recent years, significant advancements have been made in integrating innovative modular solutions into straw-bale construction technologies, aimed at replacing traditional low-tech and labor-intensive methods [26]. As it is manufactured off-site, quality control is guaranteed, and less exposure to weather conditions on site, labor intensity, and construction time are reduced.

The blown-in method is applied for thermal insulation by injecting chopped straw into wall cavities, where density and humidity need to be controlled on-site. On the other hand, biocomposite products have a high technological manufacturing process and are used as boards for insulation or cladding.

Disadvantages and considerations of the material mean that “due to its vegetal and biodegradable origin, it is necessary to guarantee the protection of liquid water and the proper regulation of water vapor to ensure durability. This fact requires adopting measures adapted to the local climate” [43]. Also, “straw is a resource whose production is seasonal. Therefore, its supply and storage must be managed” [43], which can affect or delay the execution of construction. Some disadvantages documented by the Up Straw project during public straw building construction are related to the public contract procedures, lack of experience of contractors, legislation, supply and storage of straw, and complex team coordination [73].

Straw-bale construction materials, like most bio-based alternatives, can be more expensive than traditional construction materials. However, industrialized construction systems are an opportunity to offset this cost. An analogous case can be found with timber construction, where the higher price of the solution is compensated for by the shortening of construction time, with the consequent reduction in general costs and auxiliary means.

5.3. Large-Scale Applications, Certification, and Standardization

In recent years, several large-scale projects have demonstrated the feasibility of straw-based construction in Europe, including public and multi-story buildings of up to twelve floors and over one kilometer in length. These examples highlight the potential of industrialized prefabrication to move straw beyond its traditional use in self-built rural housing.

However, significant challenges remain. The limited number of EPDs restricts comprehensive life cycle assessments and comparability among products. Moreover, the lack of harmonized European standards hinders certification and wider market adoption. Currently, professional associations are actively developing technical guidelines and certification frameworks to fill these gaps. Although straw bales are recognized as a highly effective alternative to traditional insulation materials, offering numerous advantages, their widespread adoption in the mainstream construction market remains limited due to challenges related to research, design, manufacturing, government regulations, and public perception [26]. This is also the reason behind one of the limitations of the paper, which is the limited availability of straw-based materials, EPDs, and WLCA of large projects. We expect the industry will evolve notably in this aspect in the coming years as straw construction and other bio-based materials become more widespread due to the effort to control GWP in new buildings and retrofits.

6. Conclusions

This paper aimed to comprehensively review recent advances of cereal straw as a building material for decarbonization of construction, analyzing its thermal properties, embodied carbon, and large-scale applications. The reviews focused on three levels: literature of straw as a sustainable material, commercial straw-based products (straw bales, blow-in, modular systems, biocomposites) manufacturing and properties from EPDs, and application on large-scale projects. The critical findings are as follows:

• Straw construction reuses waste from the agro-industry, such as wheat, barley, rice, and rye, and reduces the extraction of natural resources, environmental impact, energy requirements, and carbon emissions.
• This article argues that straw can reduce carbon emissions in construction, as it has biogenic carbon absorbed during plant growth and negative carbon incorporated during the extraction, transport, and manufacturing phases of derived materials. Straw-based products declared a GWP for cradle-to-gate stages (A1–A3) on a range from –101.2 to –146.5 kg CO₂-eq/m³.
• Operational carbon of straw buildings can decrease by around 60%, due to the efficient insulation of the envelope. The thermal conductivity of straw products ranged from 0.043 to 0.068 W/m·K, so less operational energy consumption is required for indoor thermal comfort.
• Product choice relates to building scale and typology. Among the four groups of products, straw bales remain common in small-scale residential housing and, in limited cases, in public buildings of up to two stories. Blow-in insulation primarily supports retrofitting and energy rehabilitation. Biocomposites can be used for insulation and finishes in both new construction and retrofit projects. Modular systems demonstrated the most balanced performance, making them suitable for large-scale applications such as public, commercial, and educational buildings, as well as multifamily housing, including high-rise or large built surfaces.
• In the last 5 years, a public building has been built in every country in Central and Western Europe, which shows a continuous development in the construction industry and administrative will. The projects range from public buildings to high-rise, renovation, and energy rehabilitation, which demonstrate possibilities and recent advances in the application of cereal straw in construction.
• This study demonstrates that prefabricated straw modules can be used on a large scale as insulation, walls, and structure, with the potential to decarbonize buildings in opaque building envelope elements. Modular systems showed greater versatility, high thermal performance, low carbon footprint, and the possibility of upscaling their application in the construction industry in Europe.
• Nevertheless, the study identifies two key limitations: (1) the scarcity of verified EPDs and standardized datasets for straw-based products; and (2) the absence of harmonized European certification frameworks. Addressing these challenges is critical for expanding their market acceptance and integration into sustainable building policies.

Straw-based materials offer a sustainable, bio-based alternative for construction. They play a key role in achieving a climate-neutral and circular building industry. Their adoption, driven by innovation, policy support, and cross-sector collaboration, could play a decisive role in reducing the environmental footprint of the built environment.

7. Future Directions

Future research should aim to further integrate straw into mainstream construction to support global efforts in reducing the building sector’s carbon footprint. Key priorities include cataloging thermal transmittance and decarbonization data for straw-based envelope components to build comprehensive, widely applicable databases. Whole life cycle assessments (WLCA) covering modules A–D are essential to capture the full carbon balance of complete buildings, alongside comparative studies with conventional materials to quantify energy savings and embodied carbon. The development of harmonized standards and expanded EPD databases will enable transparent benchmarking, supported by documentation of real-world projects across diverse regions and climates. Additional efforts should focus on in situ and laboratory measurements of chopped straw for blow-in methods and modular systems, as well as on-site monitoring, energy efficiency simulations, and publication of large-scale case studies to demonstrate progress in straw construction.