# Fabricating Sustainable All-Cellulose Composites
## 1 Introduction  
Worldwide, an ever-increasing amount of consumable materials is produced and used. At the same time, we are facing severe environmental crises: poor waste management, microplastics in all waterways, depleting natural resources, and increasing greenhouse gases in the atmosphere [1]. It is important that technological development respond to the growing demand for sustainable materials that do not intensify the current waste problem. Wood- or plant-based cellulose fibres have shown their potential as a reinforcement in composites for a relatively long time [2] alongside the commonly used glass-fibre [3] and carbon-fibre [4] reinforcements. The challenge is finding a bio-based option for the composite matrix, which is responsible for binding the fibres, transferring load, and shaping and protecting the final composite. Using wood-plastics is a step in a more sustainable direction, but they have proven been challenging to recycle [5], and therefore, they also contribute negatively to the waste problem when the material is disposed of. Furthermore, two chemically different components often have poor interfacial compatibility, which can lead to water uptake, reduction of the material's mechanical properties [6] and shortening of the lifespan of the product. One way to overcome this problem and increase recyclability is to create single-polymer composites (SPCs), where reinforcement and matrix are composed of the same materials [7]. This effectively removes the fibre-matrix adhesion challenges between different types of polymers [8]. All-cellulose composites (ACCs) can provide an environmentally friendly alternative to conventional petrochemical-based materials since they are a type of SPCs from biomass-derived cellulose, and as such, they are easily recyclable, and they originate from renewable sources. A pioneering study of ACC materials was published by [PERSON] et al. [8], who created a cellulose-based composite with good mechanical and thermal properties. Since then, there has been a growing interest in the research and development of ACC and in finding suitable solvent systems for the process [9; 10; 11; 12; 13; 14; 15]. Currently, ACCs are produced from various cellulosic raw materials (plant fibres, chemically pulped wood, textile fibres and different varieties of micro- and nano-celluloses) using different processing methods [16; 17]. All-cellulose nanocomposites (ACNC) are a subclass of nanocomposites produced using plant- and bacterial-based nanocellulose. They are manufactured via same methods as macroscale ACCs and they can improve the desired properties of the composite material such as enhance its mechanical strength [18; 19; 20; 21; 22]. Despite these recent developments, most of the recently developed ACC and ACNC materials are still produced in a laboratory scale. Cellulose-based biocomposites have already found commercial success in many industries and therefore there are also potential interests for ACC materials. Current legislation and policies also lead the way to more sustainable product manufacturing. For instance, the European Commission's Green Deal action plan [23; 24; 25] pushes the transportation industries to more sustainable practices and to generate less carbon dioxide emissions. One solution for the road transport, marine and aviation industries is to replace indoor plastic components with cellulose-based components [26]. Emission reduction occurs not only via the use of sustainable materials but through weight reduction that leads to more efficient fuel consumption [27]. In addition, low-density bio-based composites can improve key performance factors, such as impact resistance, energy absorption capacity, and reduce noise and vibration. They can also offer advantages in production cost [28].