The aim of this study was to assess the potential of utilizing Lactobacillus delbrüeckii spp. bulgaricus in order to improve the characteristics of dairy wastewater and produce biomethane. Nuclear magnetic resonance was utilized to assess the metabolites present in the unprocessed wastewater. It was determined that wastewater is a good source of important bio-refinery relevant compounds and therefore wastewater has a potential to be utilized during fermentation as nutrients source. Upon wastewater fermentation, the chemical oxygen demand and biological oxygen demand significantly decreased (respectively 97.0 and 97.8%). Protocols were tested for one- and two-stage fermentation. During the one-stage fermentation, lactic acid bacteria were not added to the wastewater. During the two-stage fermentation, acetogenesis and methanogenesis occurred separately with the addition of L. delbdueckii during the acetogenesis stage. The highest yield of methane was obtained from wastewater upon two-stage fermentation (76% two-stages compared to 38% one-stage). Therefore, L. delbrüeckii have the potential to be utilized to ferment dairy WWs and produce methane. Such treatment of wastewater not only produces methane, but also decreases the polluting effect of the waste streams, by reducing the chemical oxygen demand and biological oxygen demand to 0.199 and 0.031 g/l, respectively.

During harvesting, grain, straw, and chaff with weed seeds are separated. The chaff is returned to the fields, resulting in weed problems in the subsequent crops. We estimated the fraction of weed seeds a combine harvester could potentially harvest and used various methods to collect the chaff and treat it with heat to kill weed seeds or reduce weed seed germination. Chaff with weed seeds was placed on top of the straw and afterwards baled with the straw as a method to remove weed seeds from the field. We exposed chaff with weed seeds to exhaust gas with various temperatures and durations to study whether this heating method could be used to reduce the input of viable weed seeds to the soil during harvesting. By collecting the shed weed seeds during the growing season, we estimated that a combine harvester could potentially harvest 41%, 11%, and 100% of the seeds produced in the growing season by Bromus hordeaceus, Cirsium arvense, and Galium aparine, respectively. When the chaff was placed on top of the straw, 45% of the weed seeds stayed in the chaff fraction on top of the straw swath after one day, 35% got into the straw swath, and 20% past through the swath to the ground. Therefore, baling straw with chaff placed on the top only had a limited effect on reducing weed seed infestation. The study showed that thermal weed seed control during harvesting could potentially be applicable and incorporated in an integrated weed management approach.

This paper investigates the potential energetic utilization of wheat chaff via combustion and necessary process steps such as pretreatment and pellet production as an example of stramineous biomass. Chaff is one out of three main fractions during harvesting and remains usually on the field. Vice versa, it is a potentially so far unexploited biomass resource, which could serve as renewable energy source. Simultaneously, exploiting wheat chaff could intensify the economic benefit of agricultural land use. The combustion application requires choosing an applicable firing system adjusted to the properties of chaff. The economic feasibility of the combustion application depends strongly on the technical effort, which depends on the fuel. Chaff consists mainly of husks and straw. Due to the low ash melting point and the high chlorine content of straw, it can be advantageous for the combustion to remove short straw from the chaff by sieving. To evaluate the combustion properties of presorted and original chaff the elemental composition, the net calorific value, the volatiles and ash content and the ash melting behavior were determined. The efficient logistic of chaff is decisive for its economic exploitation. This is in conflict with the low bulk density of chaff and the resulting high storage volume. Compressing chaff into pellets optimizes its handling. This vital step for an economic exploitation of chaff was therefore investigated by this study. Parameters such as water content of the feed, addition of binders and the geometry of the pressing die bores influence the pelletizing success significantly. Thus these parameters were investigated in this study. The resulting pellets were characterized with standardized methods and compared to the requirements of EnPlus standards in terms of mechanical durability, amount of fines, bulk density and final moisture content. Finally, combustion experiments in a Large-scale Oven for Kinetics Investigation characterized the burnout behavior of the produced pellets. This was compared to pine wood pellets as conventional fuel. The performed investigations show that the pellet production and the subsequent combustion of wheat chaff pellets is a feasible approach for an energetic utilization.

Weeds are mainly controlled with herbicides in intensive crop production, but this has resulted in increasing problems with herbicide-resistant weeds and public concerns about the unwanted side-effects of herbicide use. Therefore, there is a need for new alternative methods to reduce weed problems. One way to reduce weed infestation could be to collect or kill weed seeds produced in the growing season. Crop and weeds are harvested simultaneously with the combine harvester, but most of the weed seeds are returned with the chaff to the field creating new problems in future growing seasons. During the harvesting process, the harvester produces heat. Under normal harvest conditions, the exhaust gas temperature measured directly behind the turbocharger of the engine of a combine harvester may reach between 400 °C and 480 °C depending of the size of the engine. These high temperatures indicate that there is a potential for developing a system which perhaps could be utilized to kill or damage the weeds seeds. We investigate how much heat is needed to damage weed seeds significantly and focuses on the germination patterns over time in response to these treatments. We investigated if heat treatment of weed seeds could kill the seeds or reduce seed vigour or kill the seeds before they are returned to the field. The aim is to avoid harvested viable weed seeds being added to the soil seed bank. During the threshing and cleaning process in the combine harvester, most weed seeds and chaff are separated from the crop grains. After this separation, we imagine that the weed seeds could be exposed to a high temperature before they are returned to the field. Seeds of nine common weed species were treated with temperatures of 50 °C, 100 °C, 150 °C, 200 °C, and 250 °C for 0, 2, 5, 10, and 20 s, respectively. Afterwards, the seeds were germinated for fourteen days. Seeds were differently affected by the heat treatments. We found that 50 °C and 100 °C was insufficient to harm the seeds of all species significantly at all durations. Heating with a temperature of 50 °C and 100 °C showed a slight tendency to break the dormancy of Alopecurus myosuroides Huds. and Papaver rhoeas L., but the results were not statistically significant. Seeds treated with 150 °C gave varying results depending on the duration and the weed species. The germination of A. myosuroides was significantly repressed when seeds were exposed to 250 °C for 5 s. Most species were significantly damaged when they were exposed to 250 °C for more than 10 s. Our results showed that there is a potential to explore how the waste heat energy produced by combine harvesters can be exploited to either kill or reduce the vigour of weed seeds before they are returned to the field with the chaff.