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Bioenergy from Swedish forests: A Study of extraction methods, quality and effects for forest owners
Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).ORCID-id: 0000-0002-9617-5264
2020 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The forest constitutes a very important element of renewable natural resources and makes a significant contribution to the Swedish bioeconomy. Biofuels are Sweden’s largest source of energy; of all the energy we use, 32% comes from biofuels, and of this approximately 85% comes from the forest and the forestry sector. In spite of this, logging residues constitute only a small component, compared to for example byproducts from sawmills and pulpindustry, and there is considered to be great potential for increasing their use.

In 2019 the Swedish Forestry Agency issued new recommendations for logging residue harvest and ash recycling. This was a further development of the 2008 recommendations, which formed the foundation for how forest fuel producers work today, and were based on several decades of research into, for example, the impact on forest productivity and technological development of machinery. This practice of logging residue harvest aims to yield a dry and defoliated fuel where the needles are left at the clear felled area.

However, if we are to increase the use of green renewable energy from forestry, it is very important to understand how different procurement systems affect the handling and storability of fuels from a quality perspective. It is also of great importance to understand, from the forest owners’ perspective, how removal of additional products from forestry influences nutritional balance and long-term productivity. If harvesting of logging residues does not affect long-term productivity, it is up to small-scale private forest owners to decide if removal of logging residues will be performed on their land. This thesis addresses some of these issues regarding removal of logging residues from the point of tree harvest up to the point of delivery to the energy conversion industry when the fuel chips are measured.

Regarding different methods of handling of logging residues, the traditional method – dry-stacking – was compared with the, fresh-stacking method. The logging residues investigated came from stands that mainly consisted of Norway spruce (Picea abies (L.) Karst). The loads investigated in Paper 3 also came from logging of spruce-dominated forests. Both methods aim to dry the logging residues to an acceptable moisture content for delivery to the energyconversion industry. For the later part in the supply chain, moisture content measurements of logging residues were compared during a winter and summer season.

The results of the studies indicate that the two methods do not create results that differ from what is allowed by the Swedish Forestry Agency and that they are quite similar with respect to dry mass- and nutrient removal from the clearfelled area. The results also show that similar yields and distributions of material are obtained from the logging residues with different stacking methods; in addition, the final felling itself, combined with the work performed by the forwarder operator, has a greater impact on the result than the method chosen for residue stacking of the logging residues. For the individual clear-felled area and the individual forest owner the increased removal associated with freshstacked logging residue has no major impact, however from a national perspective this small increase in removed logging residues may yield a supplement of between 0.5 – 1 TWh of green energy annually.

Regardless of treatment, the studies indicated that the delivered fuel chips will have similar characteristics. The moisture content measurement techniques currently in use are sufficiently accurate and reliable. However, if the forest owner is unlucky and an error in measurement occurs or comminution and delivery happens during an especially wet period they may suffer a significant financial loss; indeed, it is generally not under the individual forest owners’ control when the logging residues are comminuted and delivered.

Ort, förlag, år, upplaga, sidor
Växjö: Linnaeus University Press, 2020. , s. 64
Serie
Lnu Licentiate ; 30
Nyckelord [en]
logging residues, forest fuels, moisture content, needles, nutrients, moisture content measurements, Norway spruce, dry-stacking, fresh-stacking
Nationell ämneskategori
Skogsvetenskap Förnyelsebar bioenergi
Forskningsämne
Teknik, Skog och träteknik
Identifikatorer
URN: urn:nbn:se:lnu:diva-98150ISBN: 978-91-89081-87-1 (tryckt)ISBN: 978-91-89081-88-8 (digital)OAI: oai:DiVA.org:lnu-98150DiVA, id: diva2:1470308
Presentation
2020-09-25, N1017, Hus N, Linnéuniversitetet, Växjö, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2020-09-24 Skapad: 2020-09-24 Senast uppdaterad: 2022-07-08Bibliografiskt granskad
Delarbeten
1. Distributions and Losses of Logging Residues at Clear-Felled Areas during Extraction for Bioenergy: Comparing Dried- and Fresh-Stacked Method
Öppna denna publikation i ny flik eller fönster >>Distributions and Losses of Logging Residues at Clear-Felled Areas during Extraction for Bioenergy: Comparing Dried- and Fresh-Stacked Method
2015 (Engelska)Ingår i: Forests, E-ISSN 1999-4907, Vol. 6, nr 11, s. 4212-4227Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

It is well known that a large proportion of available logging residues intended for extraction will not reach the energy-conversion industry, because some are lost during transportation or left on the clear-felled area. However, there is little understanding of where logging residue losses occur in the supply chain. In this study, the distribution of logging residues for two methods (dried- and fresh-stacked method) to extract logging residues were studied in one clear-felled area. In addition, residue fractions were examined in a detailed comparison. Even though the fresh-stacked method left somewhat more logging residues at the clear-felled area, the differences are small between the methods. Approximately 30% of the total amount of logging residues was left behind between the harvester heaps, with an additional 10%-15% under these heaps and approximately 2%-3% beneath the windrows. The final product that was delivered to the energy-conversion industry was very similar, regardless of the extraction method used. The delivered chipped logging residues had moisture contents of 37% and 36% following fresh- and dried-stacked methods respectively, and in both cases the needle content in the processed logging residues was approximately 10%. However, the total amount of fine fractions (needles and fines) was slightly higher following dried-stacking.

Nyckelord
forest fuel, storage, quality, needles, moisture content, Norway spruce
Nationell ämneskategori
Skogsvetenskap Energisystem
Forskningsämne
Teknik, Skog och träteknik
Identifikatorer
urn:nbn:se:lnu:diva-48816 (URN)10.3390/f6114212 (DOI)000365704000022 ()2-s2.0-84949516879 (Scopus ID)
Tillgänglig från: 2016-01-19 Skapad: 2016-01-15 Senast uppdaterad: 2024-07-04Bibliografiskt granskad
2. Amount of nutrients extracted and left behind at a clear-felled area using the fresh-stacked and dried-stacked methods of logging residue extraction
Öppna denna publikation i ny flik eller fönster >>Amount of nutrients extracted and left behind at a clear-felled area using the fresh-stacked and dried-stacked methods of logging residue extraction
2018 (Engelska)Ingår i: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 33, nr 5, s. 437-445Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Nutrient removal has been one of the key issues since the harvesting of logging residues started in Sweden. This study examined the actual removal of nutrients by measuring the amounts of biomass removed (from a forest products perspective) combined with their respective nutrient concentrations (N, P, Ca, K and Mg), from a clear-felled area when using the dried-stacked and fresh-stacked methods. The most important finding is that the two methods were very similar regarding nutrients remaining at the clear-felled area. Of the nutrients remaining there, most were found to be well distributed between the harvester heaps. Both methods fulfilled the requirements of the Swedish Forest Agency. A sensitivity analysis showed that even if the dried-stacked method left more needles, or the fresh-stacked method extracted more logging residues, there would only be a small impact on the levels of nutrients removed. The sensitivity analysis also showed that the amount of logging residues remaining between the harvester heaps seems to be much more important for nutrients left behind, regardless of extraction method. With this in mind, it is highly probable that improvements to the extraction of logging residues, without increasing nutrient removal, can be made.

Ort, förlag, år, upplaga, sidor
Taylor & Francis Group, 2018
Nyckelord
Forest fuel; storage; quality; needles; nitrogen; Norway spruce
Nationell ämneskategori
Skogsvetenskap
Forskningsämne
Teknik, Skog och träteknik
Identifikatorer
urn:nbn:se:lnu:diva-72344 (URN)10.1080/02827581.2018.1427786 (DOI)000433155900004 ()2-s2.0-85041861691 (Scopus ID)
Tillgänglig från: 2018-04-09 Skapad: 2018-04-09 Senast uppdaterad: 2022-07-08Bibliografiskt granskad
3. The importance of accurate measurement of comminuted logging residues’ moisture contents for small-scale forest owners
Öppna denna publikation i ny flik eller fönster >>The importance of accurate measurement of comminuted logging residues’ moisture contents for small-scale forest owners
2016 (Engelska)Ingår i: Drewno, ISSN 1644-3985, Vol. 59, nr 198, s. 99-110Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Bioenergy from logging residues is an important contributor to Swedish energysupplies. Thus, accurate measurements of delivered logging residues’ energycontents are very important for both sellers and buyers. Deliveries’ energycontents are highly correlated with their moisture contents, and thus aredetermined in southern Sweden (and elsewhere) by measuring their masses andmoisture contents. There is insufficient knowledge, however, about the variation inmoisture content within and between deliveries, and hence the minimum numberof samples needed to obtain the required precision. Thus, these variations wereexamined in detail in the presented study. Nested analysis of the variance of theacquired data shows that at least nine samples are required to obtain estimates ofa delivery’s moisture content with a 3% margin of error. For high volume trade,such as that between forest companies and the energy-conversion industry,current measurement practices are sufficiently accurate. For private forest ownersmaking single deliveries, however, higher precision is required as inaccuratemeasurements can strongly affect prices.

Nyckelord
forest residues, bioenergy, forest-fuel, scaling, moisture content, private forest owners
Nationell ämneskategori
Skogsvetenskap
Forskningsämne
Teknik, Skog och träteknik; Teknik
Identifikatorer
urn:nbn:se:lnu:diva-55603 (URN)10.12841/wood.1644-3985.149.01 (DOI)000392473900008 ()2-s2.0-85010619024 (Scopus ID)
Tillgänglig från: 2016-08-18 Skapad: 2016-08-17 Senast uppdaterad: 2022-02-22Bibliografiskt granskad

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