Browsing by Subject "Biochar"

The ecological crisis is ravaging the planet. Governments and businesses have set carbon neutrality targets as part of a necessary green transformation. One promising negative emission technology is based on biochar, which has created excitement in the voluntary carbon markets. However, the voluntary carbon markets and carbon sequestration with biochar both stand at a crossroads. There is currently no regulation that would govern the markets. Only voluntary standardizations and the sellers and buyers’ conscience provide directions for the quality of offsets and real carbon cuts achieved. In addition, the production of high-quality biochar remains at a low level. This thesis contributes to the research on green transformations by examining critically the expectations and promises related to biochar and voluntary carbon markets. The focus of this study is on the framings and discourses related to the role of biochar and the voluntary carbon markets in low-carbon pathways. The main research question is: What are the different narratives and perspectives on the role of biochar and voluntary carbon markets in sustainable low-carbon pathways? To answer this, I have identified and interviewed the main actors and stakeholders in the supply chain of biochar-based offsets as well as analyzed key policy and research documents that take part in the biochar offset related discourses. The research approach draws from two theoretical frameworks: the sustainable pathways approach developed by Melissa Leach, Ian Scoones, and Andy Stirling and Maarten Hajer’s critical discourse analysis on environmental policy. These frameworks are used to analyze the informant interviews and policy and research documents. It is found out that there are five discursive patterns shaping the discourses related to biochar and the voluntary carbon markets: biochar as a magic bullet, market-led low-carbon pathway, techno-managerialism, traces of more transformative greening, and climate-centrism. Techno-managerialism is the most distinctive feature of the biochar and voluntary carbon market discourse. Together, the five patterns shape the way in which biochar and the voluntary carbon markets are perceived, how policy problems related to them are defined and framed, and finally, what type of policy solutions are formulated.

Soil carbon sequestration is one of the most promising solutions to mitigate climate change. Biochar, a carbon rich solid obtained via pyrolysis and intended to be used as a soil amendment material, is currently the most efficient tool available for carbon sequestration. Further, some biochars can also improve soil properties and increase crop yield. Before the concept of using biochar as soil amendment can be implemented in a bigger scale, it is necessary to know how biochar affects soil fauna in long term. Earthworms present one of the largest animal biomass in soil. They feed on decomposed organic matter and also biochar and transfer it to pedosphere. Effect of biochars and fertilizers on earthworm abundance, biomass and community structure was studied in two field experiments, one on fertile Stagnosol and other on nutrient deficient Umbrisol. In both study sites, split-plot experiments with four replicates were arranged. The earthworms were sampled more than four and five years after the biochar have been applied to the fields on Umbrisol and Stagnosol, respectively. No significant effect of biochar or fertilizer treatments or their interactions were found on earthworms communities, suggesting biochar to be a safe method for carbon sequestration in Southern Finland conditions. The composition of earthworm species was typical for Finnish agricultural land with A. caliginosa dominating in both soils. However further research on long-term experiments are needed, in order to fully understand mechanisms of biochar effects on earthworms.

Tiivistelmä * * Abstract Biochar is a porous carbonaceous solid material produced by pyrolysis, the thermochemical conversion of biomass in anoxic conditions. Various studies suggest that biochar amendment has a postitive effect on soil pH, soil respiration, carbon/ nitrogen ratio, nitrogen mineralization, ammonifcation and nitrification. These measurements have been studied in agricultural systems but are poorly understood in boreal forests. The study was done to investigate the effects of different wood biochar application rates: 0 t ha-1, 5 t ha-1, 10 t ha-1 on soil pH, respiration and nitrogen mineralization. Replicated studies were conducted at field sites located in Juupajoki (61⁰ 48´ N, 24⁰ 18´ E), southern Finland in young pine forest stands. The measurements were taken one year after the addition of biochar. The soil respiration ( CO2 effluxes ) were measured in June and july with different biochar ( pyrolysis temperatures 500⁰ C and 650⁰ C) while N mineralization was measured in November with biochar produced at 650 C. Biochar amendment increased soil pH in plots having biochar 10 t ha-1. Nitrogen mineralization rate in the organic layer increased with the increasing amount of biochar addition but the increase was not statistically significant. The pyrolysis temperature had no significant impact on soil CO2 effluxes. The biochar also did not have any significant impact on soil CO2 effluxes. However, in June, the plots treated with 10 t ha-1 biochar produced at 650⁰ C had significantly higher CO2 effluxes than control plots. The soil respiration data showed that biochar did not have any negative effect on native soil C stocks. We conclude that biochar exhibits important charactertics that will help carbon sequestration and N cycling in boreal forests.

Climate change and the degradation of soils are global and increasingly prevalent issue. Pyrolyzed organic materials, biochars, are progressively studied as a promising tool to sequester carbon in soils, whilst also improving soil properties. It is important to understand how different biochars affect other integral features of the soil ecosystem, such as soil biota, before they are utilized. Biochars are currently mostly utilized in agricultural settings; in order to extend their use for carbon sequestration in forest soils, more research regarding different biochars in forest settings is necessary. This Master’s thesis was conducted as literature review and meta-analysis of existing forest field studies in which the effect of biochars on soil biota was measured. Two sources (the University of Helsinki digital library collection (Helka), and internet search engine Google Scholar were used. From the studies gathered, soil respiration and microbial biomass carbon (MBC) were used as variables to estimate the effect of biochars on soil biota. Due to the scarcity of existing research, experimental conditions included in this thesis are diverse, including plantations, three climatic regions (boreal, temperate and subtropic) and different biochar types. Subgroups were formed from received data according to different treatments and standard mean differences (SMD) were compared. Contrary to the hypothesis, within this meta-analysis, soils amended with biochars demonstrated either no change or decreased soil respiration and MBC. On average, soil respiration did not show any significant change to biochar amendment, whilst MBC decreased significantly in some subgroups: short-term studies (<= 12 months), small difference in pH between soil and biochar (< 4), low pyrolysis temperature of biochar (<= 450 ˚C) and small quantity of biochar applied (< 10 t/ha). The decreasing in MBC was not consistent and diminished with increasing quantity of biochar and in study periods over 12 months. Given that biochars do not seem to have clear effects on microbial forest soil biota or microbial respiration, the application of biochars to forest soils has its potentials. However, larger scale use should be considered with caution, and further research is necessary.

Kiihtyvän ilmastonmuutoksen aikana on entistä tärkeämpää löytää tapoja vähentää päästöjä ja sitoa hiiltä. Biohiilen käyttö on yksi keino ilmastonmuutoksen hillitsemiseen, ja sillä on potentiaalia parantaa maatalouden satoja. Ennen kuin biohiilen käyttö voi yleistyä, sen mahdolliset ulkoisvaikutukset, kuten vaikutukset maaperän eliöstöön, on kuitenkin ensin selvitettävä. Tässä opinnäytetyössä tutkittiin biohiilen käytön vaikutuksia mikrobien suhteelliseen runsauteen, kastematoyhteisöihin ja mikrobibiomassaan. Vain lauhkean ja boreaalisen vyöhykkeen kenttätutkimukset olivat osana tutkimusta. Biohiilen vaikutukset mikrobiryhmien suhteelliseen määrään selvitettiin kirjallisuuskatsauksella. Kirjallisuuskatsaus tehtiin myös selvittäessä biohiilen vaikutuksia kastematoihin. Biohiilen vaikutukset mikrobibiomassaan selvitettiin meta-analyysillä. Meta-analyysissä käytetyt tutkimukset luokiteltiin muuttujien, kuten biohiilen raaka-aineen, pyrolyysilämpötilan, maaperän pH:n, SOC:n, maaperän rakenteen ja biohiilen levitysmäärän perusteella. Tätä kautta voitiin selvittää, voisiko jokin näistä muuttujista selittää meta-analyysin tulokset. Mikrobien suhteellisen runsauden havaittiin muuttuvan biohiilen lisäyksen myötä, mutta reagoivat organismiryhmät vaihtelivat suuresti ja vaikutus yleensä haihtui ajan myötä. Biohiilen lisääminen ei vaikuttanut kastematoihin merkittävästi. Meta-analyysien tulokset viittaavat siihen, että biohiilellä ei myöskään ole merkittävää vaikutusta mikrobien kokonaisbiomassaan. Eri muuttujilla tehdyt meta-analyysit viittaavat siihen, että biohiilen lisäyksellä on positiivisin vaikutus mikrobien biomassaan happamissa maaperissä, joissa on karkea rakenne ja korkea SOC-pitoisuus, kun biohiiltä tuotetaan 500 °C–700 °C:ssa ja levitetään määrinä, jotka ovat suurempia tai yhtä suuri kuin 30 t ha-1. Biohiilen raaka-aineella ei havaittu olevan merkittävää vaikutusta. Yhteenvetona voidaan todeta, että mikrobi- ja kastematoyhteisöt pysyvät yleensä vakaina biohiiltä käytettäessä. Tämä mahdollistaisi biohiilen käytön mm. hiilen sitomiseen ja maaperän hedelmällisyyden lisäämiseen maaperän eliöstöä vahingoittamatta. Lisätutkimusta kaivataan kuitenkin erityisesti boreaalisilla alueilla sekä biohiilen ja pääviljelykasvin mahdollisista vuorovaikutuksista. Tutkia kannattaisi myös mahdollisuuksia käyttää biohiiltä yhdessä muiden orgaanisten käsittelyjen, kuten lannan tai kompostin kanssa biologisen monimuotoisuuden ja sadon parantamiseksi.