An in situ Gas Generation Experiment was initiated at Olkiluoto, Finland, to simulate gas generation from low-level maintenance waste under underground repository conditions. Although the primary focus was on gas generation, the 26-year experiment also provided an opportunity to investigate carbon steel corrosion and concrete degradation upon its termination in 2023. Early heterogeneous conditions enabled the formation of microbial niches and the initiation of gas generation, despite the influence of initially high-pH cementitious water. Approximately 7% of the theoretical gas generation potential was realized over the 26-year duration of the experiment, and at the time of termination, gas production was continuing at a stabilized rate. Microbiological analyses confirmed the presence of microbial groups essential for the complete biodegradation of waste, including bacteria capable of decomposing and fermenting organic matter, as well as acetogens and methanogens. Methane and carbon dioxide were the main gases produced, with CO2 precipitating as CaCO3. Simulated disturbances, including sulphate addition and an increase in pH, had no long-term impact on gas generation. At termination, the exterior paint on the steel drums remained in surprisingly good condition, although it had become brittle and exhibited blistering. The drum interiors showed both uniform and pitting corrosion. The concrete retained its strength within the design limits, with carbonation attributed to pre-experiment storage conditions.

Paper pulp is a lignocellulosic fibrous material used in the industrial production of paper and board products. In addition to cellulose and hemicellulose, paper pulp contains 1 to 20% lignin, depending on the raw materials and pulping process used. Lignin is a heterogenous aromatic polymer that is hydrophobic and more resistant to microbial degradation compared to the easily biodegradable cellulose and hemicellulose. In this study, the biodegradation of paper pulps containing varying amounts of lignin was examined in soil and marine environments using ISO testing methods. Lignin significantly reduced the mineralization of paper pulps to CO2 in both environmental conditions, and a strong inverse correlation between lignin content and the mineralization to CO2 was observed. A similar impact was observed with natural materials containing lignin, such as birch sawdust. Since the calculation of biodegradability in most ISO and EN standards is based solely on the concept of mineralization to CO2, materials containing lignin can receive poor values in these tests. The implications of this for standardized requirements of biodegradability and possible options to overcome testing deficiencies are discussed.

Printed, flexible, and hybrid electronic technologies are advancing rapidly leading to remarkable developments in smart wearables, intelligent textiles, and health monitoring systems. Flexible electronics are typically fabricated on petroleum-derived polymeric substrates. However, in the light of global environmental concerns regarding fossil raw materials, there is a need to drive the production of flexible electronics devices based on sustainable materials. Additionally, there is a need to reduce the quantity of electronic waste by developing material recovery and recycling technologies. Here, a fully biobased and biodegradable substrate tailored for printed flexible electronic applications is developed. Based on a nanocomposite of cellulose nanofibril (CNF) and hydroxyethyl cellulose (HEC), the substrate shows excellent mechanical and optical properties for printed flexible electronics applications. High-resolution screen printing of conductive ink and typical electronics assembly processes are possible to realize on the substrate. An electrocardiograph (ECG) device is fabricated on the cellulosic substrate as a technology demonstrator and its performance is confirmed on human volunteers. Last, end-of-life scenarios are studied for printed electronic devices where device degradation and subsequent material recovery concepts are presented. This work demonstrates that sustainable plant-derived materials can play a big role toward a green transition in the electronics industry.

Flow-through columns were used to assess potential long-term trends in 90Sr biogeochemistry and transport in a Finnish near-surface very low-level waste (VLLW) repository concept. Experiments simulated the effects of water intrusion and flow through the repository barrier and backfill materials, examining impacts on 90Sr migration. Artificial rainwater containing 2.0 mg/L stable Sr (as a proxy for 90Sr) was pumped through column systems that had varying compositions from a matrix of rock flour (backfill material), bentonite (backfill/sealing material), and carbon steel (waste encapsulation material), for 295 days. Effluent geochemistry was monitored throughout. Sr retention behaviour in all column systems was broadly similar. Sr removal from influent rainwater was marked (~95% removed) at the beginning of the experiments, and this degree of removal was maintained for 20 days. Thereafter, Sr concentrations in the effluents began to rise, reaching ~2 mg/L by 295 days. Further, 56%–67% of added Sr was retained in the repository materials over the 295-day reaction period. Analysis of the effluents indicated that colloids did not form; as such, Sr output was likely to be aqueous Sr2+. Upon completion of the experiment, solid-associated Sr distribution and speciation in the columns were assessed through column sectioning and post-mortem analyses, which encompassed the following: total acid digests, sequential extractions, and XAS analysis. The total acid digests and sequential extractions showed that Sr was evenly distributed throughout the columns and that the majority (68%–87%) of solid-associated Sr was in the exchangeable fraction (MgCl2). This suggested that a major part of the solid-phase Sr was weakly bound to the column materials via outer-sphere sorption. Interestingly, a smaller amount of Sr (7%–23%) could only be extracted by aqua regia, suggesting that a proportion of Sr may bind more strongly to the barrier materials. XAS analysis of select samples confirmed that the dominant Sr phase was sorbed to the rock flour and bentonite, but not corroded carbon steel. Columns were also subject to remobilisation experiments using artificial rain- and seawater without added Sr. While rainwater remobilised Sr slowly, high-ionic strength seawater remobilised Sr at much higher rates in the systems containing bentonite. Interestingly, Sr was well retained in the rock flour-only system following rain and seawater intrusion. Overall, the results indicate that the column materials provide reactive surfaces for Sr removal should it be released from waste packages; however, the backfill and barrier materials have limited retention capacity, and the dominant sorption interaction is relatively weak. The safety case for the shallow disposal of radioactive waste should consider the possibility of seawater intrusion and that the bentonite-bound Sr was significantly more susceptible to remobilisation following seawater, despite retaining slightly more Sr during sorption experiments.

In our research on sustainable solutions for printed electronics, we are moving towards renewable materials in applications, which can be very challenging from the performance perspective, such as printed circuit boards (PCB). In this article, we examine the potential suitability of wood-based materials, such as cardboard and veneer, as substrate materials for biodegradable solutions instead of the commonly used glass-fiber reinforced epoxy. Our substrate materials were coated with fire retardant materials for improved fire resistance and screen printed with conductive silver ink. The print quality, electrical conductivity, fire performance and biodegradation were evaluated. It was concluded that if the PCB application allows manufacturing using screen printing instead of an etching process, there is the potential for these materials to act as substrates in, e.g., environmental analytics applications.

Large quantities of lignin are produced as by-streams via chemical pulping and emerging biorefinery processes. These lignins are typically water-insoluble; however, they can be converted into a water-soluble form by chemical modifications. A novel LigniOx technology solubilizes lignin using alkali-O-2 oxidation. The product can be used for bio-based dispersants. This study evaluated the biodegradability of alkali-O-2 oxidized kraft, organosolv, and hydrolysis lignin. The oxidized lignins exhibited higher biodegradation in soil and in aquatic environments in comparison to a commercial kraft lignin and a commercial lignosulfonate. In soil, the biodegradabilities of oxidized lignins were 19 to 44%, whereas the reference lignins exhibited only 5 to 12% conversion to CO2. Biodegradation of the oxidized lignins and references in the aquatic environment increased in a similar order as in the soil environment, although the degradation in each sample was slightly smaller than in the soil. The improved biodegradability of the oxidized lignins was due to the altered chemical structure of lignin. Compared to the untreated lignin, the oxidized lignin contained structures formed in aromatic ring opening reactions, making the lignin more accessible to microbial degradation. In addition, the oxidized lignin contained carbon originating from small organic compounds, which are easily biodegradable.

Bentonite is one of the materials used to construct engineered barriers in high-level radioactive nuclear waste geological disposal with its many advantageous features such as low hydraulic conductivity, self-sealing ability, durability, adsorption and immobilization of metals and radionuclides and reduction of microbial activity. Many of these properties are linked with the bentonite swelling capability. Transformations of indigenous microorganism communities from Wyoming-type bentonite and the Finnish repository site groundwater and their effects on the bentonite structural iron over five years were studied in repository relevant anoxic and oxic slurry conditions. Active sulfate reduction (0.06 nmol mL-1 day-1) was detected in the anoxic microcosm waters after a year, however after two years sulfate reduction was not active anymore. Microbial numbers determined by quantitative PCR in the bentonite slurry of both experiment types supported the finding of decrease of overall microbial activity after a year of incubation that was not maintained anymore by the dissolving organic carbon from the bentonite. Regular electron donor additions (final concentration of 2 mM for formate and acetate each, three times per year) activated the microbiome resulting in increasing numbers of bacterial 16S rRNA gene copies and sulfate reducers (dsrB gene copies) as well as detection of sulfide in the water phase of both experiment types. After 4.9 years the structural iron in the fine portion of the montmorillonite had become completely reduced in all microbial microcosms and minor smectite illitization was detected especially in anoxic microcosms. Dominating bacterial groups at the end of the experiment were mainly known sulfur/sulfate and iron reducers. Archaea and fungi constituted a minor part of the microbiomes. In originally oxic microcosms, the bacterial 16S RNA and dsrB gene copy numbers were lower than in the anoxic experiment but started to significantly increase after the electron donor additions. Microorganisms originating from the repository environment could reduce the bentonite structural iron in a few years to an extent likely to affect the bentonite swelling ability if sufficient amounts of suitable electron donors are available in localized areas where bentonite is not at high density and pressure in the geological disposal.

Spent nuclear fuel will be deposited in deep geological repositories in the crystalline bedrock in Finland and Sweden. The repositories rely on the multi-barrier KBS-3 concept, where the first barriers consist of copper-sheeted cast-iron canisters that contain the spent nuclear fuel rods. However, the repositories will be influenced by both abiotic and biotic factors. The repositories, when closed, will be flooded with a mixture of both the local groundwater and surface water and eventually return to an anoxic deep subsurface environment. This environment will contain microbial communities that utilize chemical components that have been produced both abiotically and biologically, which will determine the composition and size of the microbial communities in the repositories. Overtime, integrity of the storage canisters may become compromised due to, for example, microbially influenced corrosion, which may result from the corrosive nature of hydrogen sulfide produced in biological sulfate reduction. Radionuclides originating from the decay of the spent nuclear fuel may escape into the repository environment, from where they may diffuse further into the surface environment. In this chapter, we aim to shed light on some of the most important aspects of the Fennoscandian Shield deep crystalline bedrock biosphere identified to date, with examples of putative biogeochemical cycles that prevail in these environments.

Abstract Gas production from low- and intermediate-level nuclear waste (LLW/ILW) is important to the safety of near surface and deep geological nuclear waste repositories through the release of gaseous radionuclides and pressurization that can ultimately affect the transport of radionuclides in groundwater. The main gases generated from LLW/ILW are H2 from anaerobic corrosion of steel and CH4 from organic (cellulose) wastes. Microbes mediate CH4 generation and also can consume H2 as an energy source such as for the reduction of sulfate. A 20-year Gas Generation Experiment at Olkiluoto, Finland has furthered the understanding that microbes play in mediating gas production from LLW. The processes involved in gas generation from the experiment have been elucidated by, interpretation of gas and chemical data, DNA pyrosequencing and biogeochemical modeling. Methanogenesis develops initially mainly by utilizing hydrogen formed by anaerobic corrosion. In contrast, generation of CH4 from cellulose develops more slowly as a consequence of the complexity of the preceding cellulose degradation, fermentation processes, competition with sulfate reduction processes, and inhibition effects related to high pH and aqueous sulfide. The maximum rate of CH4 production develops after 8 years, when concrete buffered high pH regions of the experiment are neutralized by cellulose degradation and fermentation.

In Finland low level radioactive waste (LLW) contains considerable amounts of cellulose and hemicellulose-based material. Metals are also present in LLW and steel containers are used to store and dispose waste. The microbial degradation of cellulose and hemicellulose, together with the utilization of hydrogen generated by metal corrosion, will result in gas generation under final repository conditions. Microbially mediated LLW degradation and gas generation processes can influence the performance of multi-barrier systems, such as by accelerating corrosion and can affect the mobility of radionuclides from the repository. A large-scale in situ Gas Generation Experiment (GGE) was established in 1997 in Olkiluoto, Finland, to simulate the gas generation from LLW under geological repository conditions. A significant observation from the GGE was that the pH conditions were heterogeneous (pH 11 to 6), providing optimal neutral pH niches for microbial activity from the outset of the experiment. Over the extended time scale of the experiment, chemical conditions were stabilized and differences in the microbial abundances and community structure in various GGE compartments became less significant. The results demonstrate that LLW is converted to methane and carbon dioxide by a succession of anaerobic processes within a complex microbial consortium. Several genes related to cellulose and hemicellulose hydrolysis were detected using bacterial 16S rRNA gene sequencing and PICRUSt bioinformatics software. In addition, microbial groups with potential to metabolise formed saccharides to acetate, hydrogen and volatile fatty acids were detected. Hydrogenotrophic methanogens dominated after one year of operation, which was related to the utilization of hydrogen generated by anaerobic corrosion of steel and metallic waste. Acetoclastic methanogens were detected for the first time in 2005, coinciding with an increase in gas generation rate. Sulphate reducers were the most significant microbial group competing with methanogens for electron donors and their relative ratio compared to methanogens decreased considerably during the operation of the GGE. From the microbiological point of view, the results are consistent with the sequence of microbial processes simulated by previous biogeochemical modelling studies of the experiment.

In this study, we investigated the enzymatical degradability and pilot-scale composting of 14 cellulose-based materials. The materials analyzed here were cellulose regenerated from ionic liquid (EMIM[OAc]), carboxymethyl cellulose (CMC) crosslinked by aluminum salt (Al-salt), methyl cellulose, cellulose acetate, butylated hemicellulose: DS: 1, DS: 0.4, and DS: 0.2, cellophane, wet strength paper, nanocellulose, paper partially dissolved by IL, cellulose carbamate, cellulose palmitate, and cellulose octanoate. The aim of the study was to show how chemical substituting and the substituent itself influence the biodegradability of cellulose materials. The enzymatic degradation and pilot-scale composting of these films shows the correlation between the hydrolysis rate and degree of substitution. The enzymatic hydrolysis of cellulose-based films decreased exponentially as the degree of substitution increased. Modifying cellulose to the extent that it gains the strength needed to obtain good mechanical properties, while retaining its natural biodegradability is an important factor when preparing alternatives for plastic films.

Two long-term potentially oil exposed Baltic Sea coastal sites near old oil refineries and harbours were compared to nearby less exposed sites in terms of bacterial, archaeal and fungal microbiomes and oil degradation potential. The bacterial, archaeal and fungal diversities were similar in oil exposed and less exposed sampling sites based on bacterial and archaeal 16S rRNA gene and fungal 5.8S rRNA gene amplicon sequencing from both DNA and RNA fractions. The number of genes participating in alkane degradation (alkB) or PAH-ring hydroxylation (PAH-RHDα) were detected by qPCR in all water and sediment samples. These numbers correlated with the number of bacterial 16S rRNA gene copies in sediment samples but not with the concentration of petroleum hydrocarbons or PAHs. This indicates that both the clean and the more polluted sites at the Baltic Sea coastal areas have a potential for petroleum hydrocarbon degradation. The active community (based on RNA) of the coastal Baltic Sea water differed largely from the total community (based on DNA). The most noticeable difference was seen in the bacterial community in the water samples were the active community was dominated by Cyanobacteria and Proteobacteria whereas in total bacterial community Actinobacteria was the most abundant phylum. The abundance, richness and diversity of Fungi present in water and sediment samples was in general lower than that of Bacteria and Archaea. Furthermore, the sampling location influenced the fungal community composition, whereas the bacterial and archaeal communities were not influenced. This may indicate that the fungal species that are adapted to the Baltic Sea environments are few and that Fungi are potentially more vulnerable to or affected by the Baltic Sea conditions than Bacteria and Archaea.

Crystalline bedrock has been chosen for deep geologic long-term storage of used nuclear fuel in Finland. The risks generated by the deep subsurface microbial communities in these disposal sites need to be well characterised in advance to ensure safety. Deep subsurface microbial communities in a steady state are unlikely to contribute to known risk factors, such as corrosion or gas production. However, the construction of the geological final-disposal facility, bedrock disturbances, and hydraulic gradients cause changes that affect the microbial steady-state. To study the induced metabolism of deep microbial communities in changing environmental conditions, the activating effect of different electron donors and acceptors were measured with redox sensing fluorescent dyes (5-Cyano-2,3-ditolyl tetrazolium chloride, CTC and RedoxSensor™ Green, RSG). Fluids originating from two different fracture zones of the Finnish disposal site in Olkiluoto were studied. These fracture fluids were very dissimilar both chemically and in terms of bacterial and archaeal diversity. However, the microbial communities of both fracture fluids were activated, especially with acetate, which indicates the important role of acetate as a preferred electron donor for Olkiluoto deep subsurface communities.

The removal of bisphenol A and 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta[γ]2-benzopyran (HHCB), which both are widely used chemicals and known endocrine disrupters, was studied applying two biofilm processes. One of the processes was a rotating bed biofilm process (RBBR) in which waste water and small plastic pieces were rotated in cylindrical reactors by air supply. The plastic pieces served as a carrier material for biofilm as the other process, fixed bed reactor (FBR) applied wood chips. RBBR was fed with municipal waste water and FBR with artificial gray water. Preliminary results show that both experiment setups remove efficiently BOD, COD and suspended solids from waste water. BPA and HHCB were added to municipal waste water and artificial gray water to study their removal in RBBR and FBR. In RBBR, BPA removal was 10 – 29 % in the first stage and 68 – 83 % in the second stage. HHCB was removed 3 – 4 % in the first stage and 70 – 79 % in the second stage of RBBR. In FBR, the first stage removed 31 – 97 % of BPA and the second stage 80 – 100 %. 84 – 95 % and 96 – 99 % of HHCB was removed in the first and second stage, respectively. However, the percentage of removed BPA and HHCB decreased over the course of time, which refers to adsorption and saturation of BPA and HHCB to wood chips at the beginning of BPA and HHCB addition. The experiments will be continued and adaptation of microbial is expected in the latter stages of the setups. Denaturing gradient gel electrophoresis is applied to study differences in bacteria and fungi diversities in different steps of the multi-stage RBBR and FBR. In future, also 454 pyrosequencing will be applied.